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IB Biology Objectives
Option E: Neurobiology and Behaviour


Topic 1: Cells
Topic 2: The Chemistry of Life
Topic 3: Genetics
Topic 4: Ecology and Evolution
Topic 5: Human Health and Physiology
Topic 7: Cell Respiration and Photosynthesis
Topic 8: Genetics
Topic 9: Human Reproduction
Topic 10: Defense Against Infectious Disease
Topic 11: Nerves, Muscles, and Movement
Topic 12: Excretion
Topic 13: Plant Science
Option E: Neurobiology and Behaviour
Option H: Further Human Physiology

Option E.1 Introduction and Examples of Behavior

E.1.1 State that behavior of animals is related to the environmental context.

  • Behavior of animals is related to the environmental.

E.1.2 State that innate behavior develops independently of the environmental context, whereas learned behavior reflects conditions experienced by individuals during development.

  • Innate behavior develops independently of the environmental context, whereas learned behavior reflects conditions experienced by individuals during development.

E.1.3 Explain the role of natural selection in the development of behavior patterns.

  • Innate behavior patters (instincts) are inherited and are stereotyped responses to the environmental stimuli (E.3). The behavior patterns are adaptive and suit the organism to its environment. Possessing a certain gene makes it more likely that a specific behavior pattern will develop. This reflects the role of natural selection.

E.1.4 Explain, using species of birds of mammals (other than humans), one example of each of the following types of behavior: migration, grooming, communication, courtship and mate selection.

  • migration - artic tern, swallow, white stork, blue whale
    grooming - baboon
    communication - bird songs, alarm responses and hierarchal dominance patterns in wolves and red deer
    courtship - male disply (peacock, mallard duck, great crested grebe)
    mate selection - territory and song (birds) or combat (stags)

E.1.5 Explain the need for quantitative data in studies of behavior.

      • Animal behavior investigations often begin with careful observations. These help us to understand the natural history of a species. Observations often lead to the formulation of a hypothesis. To test the hypothesis, it is usually necessary to obtain quantitative data. Statistical tests can then be used to establish confidence levels for the data.



E.2 Perception of Stimuli


E.2.1   Sensory receptors act as energy transducers.


E.2.2   Human Sensory Receptors are classified as mechanoreceptors, chemoreceptors, thermoreceptors, or photoreceptors.


E.2.3   Mechanoreceptors- detect mechanical forces such as touch, pressure, vibration, stretch, and itch.   Ex. Meissners Corpuscle (light pressure, discriminative touch, vibration of low frequency)

            Chemoreceptors- respond to chemicals in an aqueous solution Ex. Olfactory Sense and the tastebuds of the tongue

            Thermoreceptors- sensitive to temperature changes Ex. sensors located in hypothalamus

            Photoreceptors- respond to light energy Ex. the retina of the eye


E.2.4   Structure of the human eye. (See attached drawing).


E.2.5   Annotated Diagram of the human retina.



E.2.6   Rod cells are more sensitive to light than cone cells, so they function better in dim light. Rod cells become bleached in bright light, but cone cells function well. Rod cells absorb all wavelengths of visible light, so they give monochrome (gray tones) vision, whereas the three types of cone cell, sensitive to red, green and blue light, give color vision. Groups of up to two hundred rod cells pass impulses to the same sensory neuron of the optic nerve, whereas cone cells have their own individual neurons through which messages can be sent to the brain. Cone cells therefore give greater visual acuity than rod cells. Rod cells are more widely dispersed through the retina (18 times more rod cells than cone cells), so they give a wider field of vision.


E.2.7   Retinal Processing- The retinal ganglion cells generate action potentials at a fairly steady rate (20-30 Hz), even in the dark.  Surprisingly, illuminating the entire retina evenly has no effect on that basal rate.  However, the activity of individual ganglion cells changes dramatically when a tiny spot of light falls on just certain portions of their receptive field.  The receptive field of a ganglion cell consists of the area of the retina that, when stimulated, influences the activity of that ganglion cell (the rods or cones that funnel their impulses to it). 

-          on-center fields- stimulated (depolarized) by light hitting the field center (the doughnut hole in the doughnut shaped cell) and are inhibited by light hitting rods in the periphery (the doughnut itself)

-          off-center fields- opposite of on-center fields for stimulation and inhibition

The mechanisms of retinal processing as currently understood can be summarized briefly as follows:

1.      The action of light on photoreceptors hyperpolarizes them.

2.      Bipolar neurons in the on regions are excited (depolarize) and excite the associated ganglion cell when the rods feeding into them are illuminated (and hyperpolarized).  Bipolar neurons in the off region are inhibited (hyperpolarize) and inhibit the ganglion cell when the rods feeding into them are stimulated.  The opposite responses of the bipolar neurons in the on and off positions indicates the fact that they have different receptor types for glutamate.

3.      Bipolar neurons receiving signals from cones feed directly into excitatory synapses on ganglion cells.  Hence, cone inputs are perceived as sharp and clear (and in color).

4.      Bipolar neurons receiving inputs from rods excite amacrine cells via gap junctions.  These local integrator neurons modify rod inputs and ultimately direct excitatory inputs to appropriate ganglion cells.  Thus, rod inputs are not only summated but are subject to detours before reaching the output (ganglion) cells.

5.      Rod inputs are also modified and subjected to lateral inhibition by synaptic (gap junction) contacts with horizontal cells.  Inputs from these local integrator cells allow the retina to convert inputs that are points of light into perceptually more meaningful contour information by accentuating bright/dark contrasts, and edges.

6.      Two varieties of ganglion cells are identified.  M cells respond best to large, moving objects at the edge of the image.  P cells relay information concerning small nonmoving objects in the center of the visual field, that is, their color and details.

Processing in the Visual Cortex

Primary visual cortex-contains an accurate topographic map of the retina; the left visual cortex receives input from the right visual field and vice versa.

-visual processing here occurs at a relatively basic level, with the processing neurons responding to dark and bright edges and object orientation

-also provides form, color, and motion inputs, with temporary areas called blobs, which forward information on to visual association areas

Prestriate Cortices- centers that continue the processing of visual information concerned with color, form, and movement

-Visual information proceeds anteriorly via parallel pathways through these areas in tow main streams.

1)                 The what processing stream extends through the ventral part of the temporal lobe and specializes in the identification of objects in the visual field.

2)                 The where processing stream takes a dorsal path through the parietal cortex all the way to the postcentral gyrus and uses information from the primary visual cortex to assess the spacial location of objects. 

-  Output from both of these regions then appears to pass to the frontal cortex, which uses the information to direct activities that, among other things, can guide movements such as reaching for a juicy peach.


Objective E.3


E.3.1   innate behavior- behavior which normally occurs in all members of a species despite natural variation in environmental influences.  Some texts refer to innate behavior as species-specific behavior.

E.3.2   Pain withdrawal reflex- (also known as the flexor reflex)- initiated by a painful stimulus (actual or percieved) and causes automatic withdrawal of the threatened body part from the stimulus.  The response that occurs when you prick your finger is a good example.  So, too, is the trunk flexion that occurs when someone pretends to throw a punch at your abdomen.  Flexor reflexes are ipsilateral, polysynaptic reflexes that involve more than one spinal cord segment- a necessity when several muscles must be recruited to withdraw the injured body part.  Since flexor reflexes are protective reflexes important to our survival, they override the spinal pathways and prevent any other reflexes from using them at the same time. Stimulates a pain receptor in the skin. The pain receptor passes a message to a sensory neuron, which carries it as a nerve impulse to the gray matter of the spinal cord. The message is passed via a linking neuron, called an association neuron in the grey matter to a motor neuron. The motor neuron carries the message to a muscle in the arm. The message stimulates the muscle to contract, pulling the hand away from the stinging plant. The muscle is called the effector. The series of neurons linking the receptor to the effector is called a reflex arc. Genes ensure that neurons in reflex arcs are connected up so that an appropriate response is made to a stimulus.


Crossed Extensor Reflex- complex spinal reflex consisting of an ipsilateral withdrawal reflex and a contralateral (opposite side) extensor reflex.  Incoming afferent fibers synapse with interneurons that control the flexor withdrawal response on the same side of the body and with other interneurons that control the extensor muscles on the opposite side.  This reflex is quite obvious when someone unexpectedly grabs for your arm.  A more common example occurs when you step barefoot on broken glass.  The ipsilateral response causes rapid lifting of the cut foot, while the contralateral response activates the extensor muscles of the opposite leg to support the weight suddenly shifted to it.  Crossed extensor reflexes are particularly important in maintaining balance. 

*ipsilateral- from and to the same side of the body (stimulus comes from one side of the body, and the response goes back to that side of the body)

*polysynaptic- reflex involving multiple synapses with chains of interneurons (neurons between sensory and motor neurons)

E.3.3   Structure of the Spinal Cord- see attached diagram

E.3.4   Pupil reflex- reflexive changes in pupil size occurring during light and dark adaptations.  Bright light shining in one or both eyes causes pupils to constrict (elicits the consensual and pupillary light reflexes).  These pupillary reflexes are mediated by the pretectal nucleus of the midbrain and by parasympathetic fibers.  In dim light, the pupils dilate, allowing more light to enter the eye interior. Photoreceptor cells in the retina detect the light stimulus. Nerve impulses are sent in sensory neurons of the optic nerve to the brain. The brainstem processes the impulses and then sends impulses to circular muscle fibers in the iris of the eye. These muscle fibers contract, causing the pupil to constrict.
conjunctival reflex- another example of a cranial reflex. If the conjunctiva is touched lightly, blinking occurs. The touch stimulus is passed to the brain along sensory neurons in the fifth cranial nerve. Messages are sent along motor neurones in the seventh cranial nerve to stimulate muscles in the upper and lower eyelids to contract and cause blinking.

E.3.5   Gross structure of the brain including the medulla oblongata, cerebellum, hypothalamus, pituitary gland and cerebral hemispheres. (See attached drawing)

E.3.6   medulla oblongata- conduction pathway between higher brain centers and spinal cord; control center for heart rate, blood vessel diameter, respiratory rate, vomiting, coughing, etc

Cerebellum- processes information from cerebral motor cortex and from proprioceptors and visual and equilibrium pathways, and provides instructions to cerebral motor cortex and subcortical motor centers that result in proper balance and posture and smooth, coordinated skeletal muscle movements

Hypothalamus- chief integration center of autonomic (involuntary) nervous system; it functions in regulation of body temperature, food intake, water balance, thirst, and biological rhythms and drives; regulates hormonal output of anterior pituitary gland and is an endocrine organ in its own right; part of the limbic system

Pituitary gland- secretes hormones that control many processes in the body

Cerebral hemispheres- cortical gray matter localizes and interprets sensory inputs, controls voluntary and skilled skeletal muscle activity, and functions in intellectual and emotional processing; basal nuclei (ganglia) are subcortical motor centers important in initiation of skeletal muscle movements

E.3.7   Brain death is clinically defined as the absence of spontaneous brainwaves.  With an EEG, the graph will show a flat line, known as a flat EEG showing the absence of brain waves and thus brain death.  Also, the pupil reflex can be used to check for brain death.  Bright light is shown to the eye of a patient in a coma or unconsciousness.  If there is no pupillary reaction (the pupils do not contract), then it is evidence that the brain stem is not processing information; evidence that the brain is dead.  This is important in determining if an unconscious patient has the ability to recover.  If the brain stem is dead and there is no pupillary reaction, there is virtually no chance of recovery.

E.3.8   taxis- a movement towards or away from a directional stimulus

kinesis- response to a nondirectional stimulus in which the rate of movement or rate of turning depends on the level of the stimulus, but the direction of movement is not affected.

E.3.9   taxes- flatworms moving towards food (chemotaxis) and Euglena moving towards light (phototaxis)

Kineses- woodlice moving about less in optimum (humid) conditions and more in unfavorable (dry) atmosphere

E.3.10 Innate behavior patterns develop independently of the environmental context. They are controlled by genes and are inherited from parents. They develop by natural selection, because they make members of a species better adapted to their environment and increase their chances of survival and reproduction. For example, taxes and kineses are behavior patterns that increase the survival chances of many invertebrates.  These are the basic instincts (ie fight or flight) that enable animals to survive in their environment.  Innate behavior is present even in humans and enables survival in all situations from primal to advanced.

Option E.4 Learned Behavior

E.4.1 Define classical conditioning.

  • Classical conditioning is an alteration in the behavior of an animal as a result of the association of external stimuli.

E.4.2 Outline Pavlov's experiments on conditioning of dogs.

  • Ivan Pavlov investigated the salivation reflex in dogs. He observed that dogs secreted saliva when they saw or tasted food. The sight or taste of meat is called the unconditioned stimulus and the secretion of saliva is called the unconditioned response. Pavlov then gave the dogs a neutral stimulus, such as the sound of ringing bell or ticking metronome, before he gave the unconditioned stimulus - the sight or taste of food. He found that, after repeating this procedure for a few days, the dogs started to secrete saliva before they have received the unconditioned stumulus. The sound of the bell or the metronome is called the conditioned stimulus and the secretion of saliva before the unconditioned stimulus is the conditioned response. The dogs had learned to associate two external stimuli - the sound of a bell or metronome and the arrival of food. This is called classical conditioning.

E.4.3 Define operant conditioning.

  • Operant conditioning is behavior that develops as a result of the association of reinforcement with a particular response, on a proportion of occasions.

E.4.4 Outline Skinner's experiments into operant conditioning.

  • Skinner designed a piece of apparatus called a Skinner box to investigate learned behavior in animals. When a rat or pigeon pressed a lever inside, a small pellet of food dropped into the box, which the rat could eat. When a hungry rat is placed onto the box it moves around, looking and sniffing at everything within the box. It eventually presses the lever by accident, but soon learns to associate pressing the lever with the reward of food. The food reward is called the reinforcement. Pressing the lever is called the operant response. This form of learning is called trial and error learning or operant conditioning. The more quickly the reinforcement is given, the more quickly the operant response develops. Surprisingly, Skinner found that if the reinforcement conditioning develops more strongly than if the reinforcement is always given.

E.4.5 Define imprinting.

  • Imprinting is learning a response to a stimulus during a sensitive period of development.

E.4.6 Outline Lorenz's experiments on imprinting in geese.

  • Lorenz investigated learning sing greylag geese and other birds. In one experiment, he removed half of the eggs that a female goose had laid and kept them in an incubator. Lorenz was with the goslings when they hatched out from those eggs, and he remained with them for a few hours. He was therefore the first moving object that they saw. The goslings did not show normal behavior - they followed him around instead of their mother and some of them even tried to mate with humans when they became adults.

E.4.7 Discuss how the process of learning improves the chances of survival.

  • There are many situations where survival chances can be increased as result of learning: Birds learn to avoid the evil-tasting black and orange caterpillars of the cinnabar moth by conditioning.
    Grizzly bears learn by operant conditioning how to catch salmon.
    Goslings learn who their mother is by imprinting and so avoid predators by remaining close to her.

Option E.5 Social Behavior

E.5.1 List three examples of animals that show social behavior.

  • Ants, honey bees, and termites.

E.5.2 Describe the social organization of honey bee colonies.

  • There are three castes of honey bees each of which has different tasks. The single queen bee is normally the only member of the colony to lay eggs. The worker bees do all the jobs that are needed to maintain the colony. The drones do nothing to help the colony to survive, but if they successfully mate with virgin queens they spread the genes of the colony to new colonies. Workers eject drones from the colony at the end of the season during which virgin queens are available.

E.5.3 Discuss the role of altruistic behavior in social organizations using two examples.

  • NOTE: Parental care is not considered to be altruism.

E.6 The ANS (Autonomic Nervous System)

E.6.1- The ANS consists of sympathetic and parasympathetic motor neurons.


E.6.2- The roles of the sympathetic and parasympathetic system are largely antagonistic.


E.6.3- The ANS serves the heart, blood vessels, digestive system, and smooth muscles.


E.6.4- Sympathetic and Parasympathetic System


The sympathetic system takes over in emergency situations and provides the correct body responses to respond to the situation.  The parasympathetic system maintains the correct resting states of organs and helps with energy conservation.  In a fight-or-flight situation, the sympathetic division increases the respiratory and heart rates, while inhibiting digestion and elimination.  When the emergency is over, the parasympathetic division restores heart and breathing rates to resting levels and then attends to processes that refuel body cells and discard wastes.  The sympathetic system is the major actor in controlling of blood pressure, even at rest.  The blood vessels are kept in a continual state of partial constriction called vasomotor tone.  When faster blood delivery is needed, sympathetic nerve fibers deliver impulses more rapidly, causing blood vessels to constrict and pressure to rise.  When blood pressure is to be decreased, the vessels are prompted to dilate.  Parasympathetic effects are seen mainly in the heart and smooth muscle of digestive and urinary tract organs.  The parasympathetic division slows down the heart and dictates the normal activity levels of the digestive and urinary tracts.  However, the sympathetic division can override these parasympathetic effects in times of stress. 

-          Iris of the Eye- Parasympathetic system stimulates the constrictor muscles, constricts eye pupils; Sympathetic system- stimulates dilator muscles, dilates eye pupils

-          Salivary glands- Parasympathetic system- stimulates secretory activity; Sympathetic system- inhibits secretory activity, causes vasoconstriction of blood vessels supplying the glands

-          Heart Muscle- Parasympathetic system- decreases rate, slows and steadies heart; Sympathetic system increases rate and force of heartbeat

-          Heart: coronary blood vessels- parasympathetic constricts coronary blood vessels; sympathetic causes vasodilation


E.6.5- Conscious vs. Automatic Reflexes


Bladder control involves both the conscious part of the brain and automatic reflexes.  A body reflex will signal the brain when the bladder is full and the person needs to urinate.  However, the person has a certain amount of conscious control over when he urinates.  Up to a certain point, a person can hold it and consciously choose not to use the restroom.  However, eventually the automatic reflexes will kick back in when the bladder gets too full for conscious control to prevent urination and the reflex will force urination.  Also, some people lose conscious control of the bladder for whatever reason and only the automatic reflex of the full bladder controls their urination.


Option E.7- Neurotransmitters and Synapses


E.7.1   The synapses of the peripheral nervous system (PNS) are classified according to neurotransmitter used, including acetycholine and noradrenaline.


E.7.2   Presynaptic neurons can either encourage or inhibit postsynaptic transmission by depolarization or hyperpolarization of the postsynaptic membrane.

Postsynaptic Excitation and Inhibition

Excitatory Synapses- At excitatory synapses, neurotransmitter binding causes depolarization of the postsynaptic membrane.  In contrast to many channels opened on axonal membranes, only one type of channel opens on postsynaptic membranes (membranes of dendrites and neuronal cell bodies).  This channel often allows Na+ and K+ ions to diffuse simultaneously through the membrane in opposite directions.  Because the electrochemical gradient for Na+ is much steeper than that for K+, the influx of sodium through the one channel is greater than the efflux of potassium, and net depolarization occurs.  Result is excitatory postsynaptic potentials (ESPSs) that occur at postsynaptic membranes, and, if their current is strong enough when they reach the axonal hillock, they can cause generation of an action potential.

Inhibitory Synapses- binding of neurotransmitters at inhibitory synapses reduces a postsynaptic neurons ability to generate an action potential.  Most inhibitory neurotransmitters induce hyperpolarization of the postsynaptic membrane by making the membrane more permeable to potassium ions, chloride ions, or both.  Sodium ion permeability is not affected.  If potassium gates are opened, potassium ions move out of the cell; if chloride gates are opened, chloride ions move in.  In either case, the charge on the inner face of the membrane becomes relatively more negative.  As membrane potential increases and is driven further from axons threshold, the postsynaptic neuron becomes less and less likely to fire and larger depolarizing currents are required to induce an action potential.  Such potential changes are called inhibitory postsynaptic potentials (ISPSs).

Presynaptic Inhibition- occurs when the release of excitatory neurotransmitter by one neuron is inhibited by the activity of another neuron via an axoaxonic synapse.  More than one mechanism is involved, but the end result is that less neurotransmitter is released and bound, and smaller ESPSs are formed.  In contrast to postsynaptic inhibition by ISPSs, which decreases the excitability of the postsynaptic neuron, presynaptic inhibition is more like a functional synaptic pruning.  It reduces excitatory stimulation of the postsynaptic neuron by the presynaptic neuron.

Neuromodulation- occurs when a neurotransmitter acts via slow changes in target cell metabolism, or chemicals other than neurotransmitters modify neuronal activity.  Some neuromodulators influence the synthesis, release, degradation, or reuptake of neurotransmitter by a presynaptic neuron.  Others alter the sensitivity of the postsynaptic membrane to the neurotransmitter.  Many neuromodulators are hormones that act at sites relatively far from their release site.


E.7.3   Pain Reception- principal pain receptors are the several million bare sensory nerve endings that weave through all the tissues and organs of the body (except the brain) and respond to noxious stimuli (anything damaging to tissues).  Wherever body tissue is injured, the damaged cells release and inflammatory soup of chemicals including bradykinins, the most potent pain-producing chemicals known.  Bradykinins, in turn, unleash the production of an avalanche of inflammatory chemicals, such as histamines and prostaglandins, that initiate healing.  Also, ATP released from injured cells into the extracellular space may stimulate pain receptors on small-diameter C fibers, thus initiating pain signals.  Pain in impulses travels along the small, unmyelinated C fibers either directly to the thalamus (allowing the sensory cortex to analyze what hurts and how much), or over several synapses in the spinothalamic tract, traveling through brain stem, hypothalamus, etc before reaching the thalamus.

            Endorphins and enkephalins- act as natural opiates, reducing our perception of pain under certain stressful conditions. (Enkephalin activity increases dramatically in pregnant women in labor.  Endorphin release is enhanced when an athlete gets a so-called second wind and is probably responsible for the runners high.  Also, some claim that the placebo effect is due to endorphin release.)


E.7.4   Symptoms of Parkinsons Disease:

-          persistent tremor at rest (exhibited by head nodding and a pill-rolling movement of their fingers.)

-          a forward-bent walking posture and a shuffling gait

-          stiff facial expression

-          slow in initiating and executing movement

Parkinsons disease results from a degeneration of the dopamine-releasing neurons of the substantia nigra, a brain stem nucleus that projects to the corpus striatum.  As the substantia nigra neurons deteriorate, the dopamine-deprived basal nuclei they target become overactive, causing the well-known symptoms of the disease.  One current treatment is the use of L-dopa, which is used in combination generally and converts to dopamine in the brain.  However, L-dopa has many undesirable side effects: severe nausea, dizziness, and, in some, liver damage.


E.7.5   A Psychoactive Drug is a chemical that alters perceptions and mood. There are three categories of Psychoactive Drugs: Depressants, Stimulants, and Hallucinogens. Psychoactive Drugs do their work at the brain's synapses, by stimulating inhibitors, or mimicking the activity of neurotransmitters, the brain's chemical messengers.

Decreased synaptic transmission occurs by the stimulation of inhibitors in the synapses (used in depressants for example).

Increased synaptic transmission occurs when the drugs mimic the activity of neurotransmitters, overstimulating neurons (used in stimulants and hallucinogens).

In drug use, the neurons alternately stop and start producing neurotransmitter.  During the effective period of the drug, emotion is high, but the emotion level drops after drug use due to lack of neurotransmitter.

E.7.6   Nicotine- increased alertness and improved short-term memory, negatively-Increases in blood pressure and heart rate, faster respiration, constriction of arteries, stimulation of the central nervous system.




Cocaine- a feeling of euphoria, excitement, reduced hunger, and a feeling of strength: after high of about an hour, user crashes and feels depressed, anxious, and paranoid; then the addict goes into a period of exhaustion and may sleep for a very long time Negative- dizziness, headache, movement problems, anxiety, insomnia, depression, hallucinations- can cause increase in blood pressure, stroke or even DEATH




Amphetamines- cause the release of dopamine from axon terminals, block dopamine reuptake, inhibit the storage of dopamine in vesicles, inhibit the destruction of dopamine by enzymes. Increased heart rate, increased blood pressure, reduced appetite, dilation of the pupils, feelings of happiness and power, reduced fatigue are short term effects.  

Insomnia, restlessness, "Paranoid psychosis," Hallucinations, Violent and aggressive behavior, Weight loss, and Tremors are long-term effects.


E.7.7   Benzodiazepines- (Valium and Temazepam) Depressant- from relaxation, lowered inhibitions, reduced intensity of physical sensations, digestive upsets, body heat loss, reduced muscular coordination to passing out, loss of body control, stupor, severe depression of respiration, and possible death. (Effects are exaggerated when used in combination with alcohol - synergistic effect).  After prolonged use of large amounts, amnesia, confusion, drowsiness, and personality changes.




Cannabis- (marijuana, reefer, weed, hashish, pot, grass, MJ, Mary Jane, etc) Effects on CNS- relaxation, reduced coordination, reduced blood pressure, sleepiness, disruption in attention, and an altered sense of time and space...a good reason not to drive or operate machinery while under the influence.  In high doses, it can cause- hallucinations, delusions, impaired memory, and disorientation.



Alcohol- Effects range from relaxation, lowered inhibitions, reduced intensity of physical sensations, digestive upsets, body heat loss, reduced muscular coordination to loss of body control, passing out (also causing physical injuries), susceptibility to pneumonia, and cessation of breathing.  Prolonged use of large amounts can cause liver damage, ulcers, chronic diarrhea, amnesia, vomiting, brain damage, internal bleeding, and debilitation.