Download Nervous System

Human Body Systems
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Organization of the Body (Review)
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Basic unit of structure and function
Tissues
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Group of cells that perform a single function
(e.g. epithelial, connective, nervous, muscle)
Organs
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Different types of tissues that work together to perform
a closely related function (e.g. eye, liver, lungs)
Organ Systems
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Group of organs that perform closely related functions
(e.g. circulatory, respiratory, digestive)
Homeostasis
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Cells
Definition: the process by which organisms keep internal
conditions relatively constant despite changes in their
external environments
Requires the integration of all organ systems at the same time
Nervous system in conjunction with the endocrine system
(hormones) is responsible for this integration
Positive feedback – your body’s response results in an increase in
the effect of the stimulus, (e.g. the flight-fight response)
Nervous System
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Recognizes and coordinates the body’s response to changes in its
internal and external environments.
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General Functions of the Nervous System
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Sensory input – vision, hearing, balance, smell, taste, and
touch
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Motor output – muscle contraction and movement
Memory and integration of information
Division of Labor
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Central Nervous System (CNS)
Control center of the body that relays messages, and processes
and analyzes information
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Brain
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Cerebrum – largest region; right and left
hemispheres that are connected by corpus callosum;
voluntary activities and higher brain functions
Cerebellum – located at the lower back part of brain;
coordination and balance
Brain stem – connects the brain and spinal chord; two regions:
pons and medulla oblongata, control breathing, heart rate and
swallowing
•Thalamus:
Thalamus and hypothalamus - between brain stem and cerebrum
relay station for sensory info
Hypothalamus: most important homeostatic site; hormones, body’s
thermostat, fight or flight, thirst, hunger, reproduction
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Spinal Cord
Two main functions:
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Processing of simple responses to certain stimuli
(reflexes)
Carries info to and from brain to body
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Peripheral Nervous System (PNS)
Receives information from the environment and relays to and from
CNS and sensory, motor and gland cells
Two divisions:
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Sensory - Made of sensory neurons that bring info to the CNS
Motor - Made of sensory neurons that convey info from the CNS;
two subdivisions
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Somatic (voluntary): respond to external stimuli
Autonomic (involuntary): respond to internal stimuli
w/the parasympathetic and sympathetic divisions
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Parasympathetic ↓energy consumption
Autonomic Overview Movie
Neurons (Nerve Cells)
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Specialized cells that carry electrical signals called impulses
(Draw Fig. 35-5; pg. 897)
3 Types of Neurons:
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Sympathetic ↑energy consumption
Sensory – carry impulses from the sense organs to the
spinal cord and brain
Motor – carry impulses from brain and spinal cord to
muscles and glands
Interneurons – Connect sensory and motor neurons and
carry impulses between them
Anatomy of a Neuron
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Cell Body
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Largest part of the neuron
Contains the nucleus and most of the cytoplasm
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Carry impulses from the environment or other neurons
to the cell body
Long fiber that carries impulses from the cell body
Ends in axon terminals that contain vesicles for
neurotransmitters
Myelin Sheath
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Insulates the axon
Gaps in the myelin sheath allow an impulse to jump from node
to node, thus increasing its speed
The Nerve Impulse
The Resting Neuron
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Dendrites
Axon
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Metabolic activity takes place in the cell body
At rest, the
inside has a
the resting
(-70mVolts,
outside of the cell has a net positive charge and the
net negative charge. This charge difference is called
potential.
about 5% of the voltage in AA battery)
The charge difference is created by active transport of ions across
the cell membrane via the sodium-potassium pump.
Sodium ions (Na+) are pumped outside the cell and potassium (K+)
ions are pumped into the cell.
The Moving Impulse
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An impulse begins when a neuron is stimulated by the axon of
another neuron or by the environment.
Na+ pores open and the flood of Na+ ions makes the inside
positive. This reversal of charges, from negative to positive
is called a nerve impulse, or an action potential.
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Nerve Impulse Pathway Overview
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Impulse is received by the dendrites from the environment or another
neuron, then gets rapidly channeled through the cell body to the
axon
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Axon branches out into axon terminals, which contain tiny vesicles
filled with neurotransmitters, which are chemicals used by a neuron
to transmit an impulse to another cell. (e.g. acetylcholine,
serotonin, dopamine and adrenalin).
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Vesicles release neurotransmitters into the open space between
neurons called the synapse.
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As the impulse passes, K+ pores open and K+ flows out which
restores the resting potential (charge difference)
The neurotransmitters diffuse across the synapse and attach
themselves to receptors on dendrite of neighboring cell
Reflexes
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Reflexes are automatic responses to stimuli
Controlled by 5-part reflex arc:
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Sensory receptors on finger reacts to stimulus (heat)
Impulse is carried to the spinal cord by a sensory neuron
In the spinal cord, the impulse is transferred by an
interneuron to motor neuron
Motor neurons conducts the impulse to an effector (arm
muscles)
Effector responds to the impulses by contracting (hand
gets pulled away from the heat)
The Senses
5 General Sensory Receptors: pain, thermo-, mechano-, chemoand photoreceptors. Vision
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Hearing and Balance
Smell and Taste
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Nervous System Disorders
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Touch
Migraine Headaches – caused by change in serotonin levels?
(affected by caffeine, estrogen, certain foods)
Parkinson’s –caused by damage to dopamine transmitters; causes
uncontrollable shaking, no cure
Tay-Sachs –lack enzyme to break down fatty deposits in the
brain; neurological deterioration; death by age 4-5
Dementia - damaged brain cells caused by injury or disease
(Alzheimer’s); memory loss and personality change.
Drugs and the Nervous System
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Stimulants
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Accelerate HR, BP, and breathing rate
Increases the release of neurotransmitters; leads to
release of energy and feeling of well-being
When effect wears off, brain’s supply is depleted
Caffeine
Cocaine
Methamphetamines
Depressants
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Slow down HR, lower BP and breathing rate, relax muscles
and relieves anxiety
Alcohol
Marijuana
Sleeping Pills