Bio Exam 3- Animal Nervous System

Nerve Net

a diffuse arrangement of cells

Central Nervous System

large numbers of neurons aggregated into clusters (ganglia)

Central Nervous System

→brain

→brain steam

→spinal cord

Peripheral nervous system

all neurons and other component that are outside of the CNS

Afferent nervous system (Sensory)

brings sensory info to CNS

Efferent Division (Motor)

carries signals from CNS to effectors

Somatic Nervous System

carries out voluntary responses

→skeletal muscles are effectors

Autonomic Nervous System

Carries out involuntary responses

→smooth muscles, cardiac muscles, and glands are effectors

Sympathetic nervous system (fight or flight)

promotes increased support of physical activity inhibits digestion

Parasympathetic nervous system (rest and digest)

promotes digestion, reduced activity

sensory neurons

carry information to the CNS

interneurons

cells in the CNS that integrate info from the sensory neurons

motor neurons

cells that sends signals to effectors cells in glands and muscles

nerves

sensory neurons and motor neurons are bundles into long strands of nervous tissue

Soma

contains the nucleus

dendrites

short projections that recieve signals form the axons of other neurons

axons

long projections that send signals to the dendrites of other neurons

synapse

space between adjacent neurons

voltage or electrical potential

a difference in charge

membrane potentials

a difference in charge across a membrane

resting potential

negative inside cell relative to outside

resting potential

3 Na+ ions are pumped out of the cell and 2 K+ ions are pumped into the cell

action potential

a rapid temporary change in a membrane potential

depolarization

the membrane becomes less polarized that when it is at its resting potential

threshold potential

channels open allowing ions to flow across the membrane

repolarization

some ion channels are closed and others are open

hyperpolarization

Vm is slightly more negative than resting potential

axon diameter

faster propagation in larger axons

myelination

the presence of specialized accessory cells (glia) that wrap around axons and form a myelin sheath

CNS

oligodendrocytes

PNS

schwann cells

myelin sheath

prevent ions from leaking out of the axon

node of raniver

many K+ and Na+ channels

→next AP propagated here

Ligand gated channel

opens in response to the binding of a specific Neurotransmitter

Neuronal Intergration

summation allows input from multiple presynaptic neurons to influence the post synaptic neuron