BIOL 365 Nervous System

Major functions of the nervous system

The controlling, regulatory, and communicating sytem in the body; in conjuntion with the endocrine system is to maintain body function and homeostasis (fast-acting)

Central Nervous System

brain and spinal cord

Peripheral nercous system

all peripheral nerves

Neuron

basic cellular unit of the nervous system

Dendrites

branched receptors of the neuron to recieve signals

Axon

long, and carries impluse away from the cell body

Sensory neurons (afferent)

sense the environment and take sensory info to the CNS

Interneurons (99% of all neurons)

Connect neurons together in CNS (intergrate info)

Motor neurons (efferent)

Recieve info from CNS and takes it to effector organs to trigger a response

Characteristics of a nerve impulse

occur in response to stimulus, produced by changes in membrane potential, all-or-none responses, signal intensity is signaled by frequency of impulses

Schwann Cell

Produce insulating mylin sheath to help maintain impulse down the axon

How an impulse is produced

resting potentials (high K+ inside axon and Na+ outside axon maintained by pump), voltage change opens Na+ permeable channels and membrane depolarizes, repolarizes when K+ channels open

Characteristics of nerve propogation

small axons conduct slowly, axons are bigger where fast responses are needed, vertebrates increase propagation speed with myelination (charge propagates by saltatory movement)

Nerve synapse

sites where signals are transmitted from one neuron to another (electrical and chemical)

Electrical synapse

charge flows across “gap-junction”, no time lag (therefore very fast), good for escape reactions

Chemical synapse

use specialized neurotransmitters that diffuse from one membrane to the other to propagate signal

Invertbrate nervous system

not complex, very basic (nerve nets rather than central nervous system)

Vertebrate nervous systems

Nerves interconnecting spinal cord and brain, spinal cord hasn’t changed much over evolution, cerebrum becomes elaborated further down the lineages

increase

Brains ________ with body size (but not a 1:1 ratio)

olfactory

Birds’ _______ region in the brain is greatly reduced

optic

Birds’ _______ lobes are enlarged

developed

In mammals the olfactory is very ________

_______ can generate fresh supplies of brain cells

Adult canaries and zebra zinches

Traits of the peripherial nervous system

Motor and sensory neurons are bundled, two subdivisions (somatic and autonomic)

Autonomic nervous system

Made up of Parasympathetic and sympathetic systems (maintain balance of homeostasis)

Parasympathetic system

lowers heart rate and respiritory rates

sympathetic system

increases heart rate and respiratory rate

Somatic nervous system

innervates skeletal muscles for movement impulses

Reflex arc

neurological feedback loops, only 2 or 3 neurons, bypasses brain