Biology & BehaviorThe Brain, The Nervous System & the Glands

The Neurons and the NeurotransmittersNeurons

the specialized cells that conduct impulses through the nervous system and contain three major parts - a cell body, dendrites, and an axon

anatomy of a neuroncell body (soma) contains the nucleus and carries out the metabolic, or life-sustaining, functions of a neuron.

dendrites (comes from the Greek word for "tree") and are the primary receivers of signals from the neurons, they look life the leafless branches of a tree

axon is the slender, tail-like extension of the neuron that transmits signals to the dendrites or cell body of other neurons and to muscles, glands, and other parts of the body

works of neurons

afferent (sensory) neurons relay messages from the sense organs and receptors - eyes, ears, nose, mouth, and skin -- to the brain or spinal cord;

efferent (motor) neurons convey signals from the central nervous to the glands and the muscles, enabling the body to move

interneurons (thousand of times more numerous than motor or sensory neurons) carry information between neurons in the brain and between neurons in the spinal cord

Glial Cells are specialized cells in the brain and spinal cord that hold the neurons together, remove waste products, such as dead neurons, from the brain by engulfing and digesting them, and they handle other manufacturing, nourishing and cleanup tasks smaller than neurons and make up more than one-half the volume of the human brain

The Synapse is the junction where the axon terminal of a sending neuron communicates with a receiving neuron across the synaptic cleft.

The Myelin Sheath is a white, fatty coating, wrapped around some axons that acts as insulation

Neurotransmitters

Neurotransmitter is a chemical substance that is released into the synaptic cleft from the axon terminal of a sending neuron, crosses a synapse, and binds to appropriate receptors sites on the dendrites or cell body of a receiving neuron, influencing the cell either to fire or not to fire

why synaptic vesicles can continue to pour out

the cell body of the neuron is always working to manufacture more of the neurotransmitters

unused neurotransmitters in the synaptic cleft may be broken down into components and reclaimed by the axon terminal to be recycled and used again

the process of REUPTAKE - the neurotransmitter is taken from the synaptic cleft back into the axon terminal, intact and ready for immediate use thus terminating the neurotransmitter's excitatory or inhibitory effect on the receiving neuron

the variety of neurotransmitters

acetylcholine (Ach), a neurotransmitter that exerts excitatory effects on the skeletal muscle fibers, causing them to contract so that the body can move and has an inhibitory effect on the muscle fibers in the heart, which keeps the heart from beating too rapidly

Dopamine (DA), one of four neurotransmitters called monoamines, produces both excitatory and inhibitor effects and is involved in several functions, including learning, attention, movement, and reinforcement

Norepinephrine (NE) has an effect on eating habits (it stimulates the intake of carbohydrates) and plays a major role in alertness and wakefulness.

Epinephrine complements norepinephrine by affecting the metabolism of glucose and causing the nutrient energy stored in muscles to be released during strenuous exercise

Serotonin plays an important role in regulating mood, sleep, impulsivity, aggression, and appetite

Glutamate is the primary excitatory neurotransmitter in the brain

GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the brain

Endorphins provide relief from pain or the stress of vigorous exercise and produce feelings of pleasure and well-being

The Nervous Systemthe Central Nervous System & the Peripheral Nervous System

2 divisions of the human nervous system

Central Nervous System (CNS) - composed of brain and the spinal cord

Peripheral Nervous System - connects the central nervous system to all other parts of the body

why is an intact spinal cord important to normal functioning?

the spinal cord is an extension of the brain that reaches from the base of the brain, through the neck, and down the hollow center of the spinal column; it transmits messages between the brain and the peripheral nervous system

the brainstem

brainstem is part of the hindbrain that begins at the site where the spinal cord enlarges as it enters the skull, and it handles functions that are so critical to physical survival that damage to it is life-threatening

medulla is the part of the brainstem that controls heartbeat, breathing, blood pressure, coughing, and swallowing

reticular formation (reticular activating system RAS), plays a crucial role in arousal and attention

the Cerebellum

important to the body's ability to execute smooth, skilled movements

regulates muscle tone and posture

coordinates the series of movements necessary to perform many simple activities without conscious effort

help to heighten ability to focus attention on incoming sensory stimuli and to shift attention

may increase our efficiency in acquiring sensory information and discriminating between sensory stimuli

the Midbrain

lies between the hindbrain & the forebrain

act as relay stations through which the basic physiological functions of the hindbrain are linked to the cognitive functions of the forebrain

substantia nigra is located in the midbrain and is comprised of darkly covered nuclei of nerve cells that control our unconscious motor actions.

the thalamus & hypothalamus

thalamus has two egg-shaped parts, serves as relay station for virtually all the information that flows into and out of the forebrain, including sensory information from all the senses except smell

hypothalamus regulates hunger, thirst, sexual behavior, and a wide variety of emotional behaviors, and internal body temperature

the Limbic Systemgroup of structures in the brain, including the amygdala and the hippocampus, that are collectively involved in emotional expression, memory, and motivation.

amygdala plays an important role in emotion, particularly in response to unpleasant or punishing stimuli

hippocampus is located in the interior temporal lobes and plays a central role in the storing of new memories, the response to new and unexpected stimuli, and navigational ability

plays a role in the brain's internal representation of space in the form of neural maps

the cerebrum

most essential part of the brain is the cerebrum & its cortex

cerebrum is the largest structure in human brain. it is composed of two cerebral hemisphere, the left & right which control movement & feeling on the opposing side of the body

corpus callosum connects the two hemisphere and makes possible the transfer of information and the coordination of activity between them

cerebral cortex is the thin gray outer covering about 1/8 inch thick. it is primarily responsible for the higher mental processes of language, memory & thinking

Cerebral cortexgray outer covering about 1/8 inch thick and is primarily responsible for the higher mental processes

contain sensory input areas where vision, hearing, touchy pressure, and temperature register

motor areas, which control voluntary movement

association areas house memories and are involved in thought, perception, and language

4 lobes of the cerebral hemisphere

motor cortex - a strip of tissue at the rear of the frontal lobes that controls voluntary body movement

plasticity - the brain's capacity to adopt to changes such as brain damage - of the motor cortex is maintained throughout life

broca's area - involved in directing the pattern of muscle movement required to produce speech sounds in the left hemisphere of the brain

frontal association areas -involves thinking, motivation, planning for the future, impulse control, and emotional responses

frontal lobes - begin at the front of the brain and extend to the top center of the skull. they contain the motor cortex, Broca's area, and the frontal association

areas

the Parietal Lobes - lie directly behind the frontal lobes, in the top middle portion of the brain and are involved in the reception and processing of touch stimuli

somatosensory cortex,, the site where touch, pressure, temperature, and pain register in the cerebral cortex

the Occipital Lobes at the rear of the brain are involved in the reception and interpretation of visual information

at the very back of the occipital lobes is the primary visual cortex, the site where vision registers in the cortex

the Temporal Lobes, located slightly above ears, are involved in the reception and interpretation of auditory stimuli. the site in the cortex where the hearing registers is known as the primary auditory cortex

wernicke's area - is located adjacent to the primary auditory cortex in the left temporal lobe. this is the language area involved in comprehending the spoken word and in formulating coherent written and spoken language

wernicke's asphasia is a type asphasia resulting from damage to wernicke's area

wernicke's patient when asked how he was feeling, replied " i that there's an awful lot of mung, but i think i've a lot of net and tunged in a little wheat duhvayden" (Buckingham & Kertesz, 1974)

auditory asphasia (word deafness) - the person may hear normally but may not be able to understand spoken language

the cerebral hemisphereLeft hemisphere - handles most of the language functions, including speaking, writing, reading, speech comprehension, and comprehension of the written information

Right Hemisphere - (controlling the left side of the body) more adept at visual spatial relations

auditory cortex in the right hemisphere appears to be far better able to process music that the left

augments left hemisphere's language-processing activities'/ (figures out what its meant and who says it) (e.g the balancing act)

the right hemisphere's role in emotion

responds to the emotional message conveyed by another's tone of voice

reading and interpreting nonverbal behavior

involve in the expression of emotion through tone of voice and facial expression

brain mechanisms responsible for negative emotions are located in the right hemisphere

the Peripheral Nervous System

PNS is made up of all the nerves that connect the central nervous system to the rest of the body

2 subdivisions of the PNS

somatic nervous system -

(1) compose of all the sensory nerves which transmits information from the sense receptors - the eyes, ears, nose, tongue, and skin -- to the central nervous system,

(2) all the motor nerves, which relay messages from the central nervous system make it possible for you to sense your environment and to move, and they are primarily under conscious control

autonomic nervous system -

operates without any conscious control or awareness

transmits messages between the CNS and the glands, the cardiac (heart) muscle, and the smooth muscles (such as those in the large arteries and the gastrointestinal system)

ANS is further divided into 2 parts - the sympathetic & the parasympathetic nervous system

sympathetic nervous system automatically mobilizes the body's resources, preparing you for action

parasympathetic nervous system brings these heightened bodily functions back to normal

the Endocrine System

Endocrine system is a series of ductless glands located in various parts of the body, that manufactured and secrete the chemical substances known as hormones, and secrete them into the bloodstream, thus affecting cells in other parts of the body