Chapter 12 - Nervous System Flashcards
Functions of the Nervous system
- Sensory input - gathers info & makes us aware of what’s happening
- Integration - processes & interprets info
- Motor output - produces response in body; away from brain to responding organ
Central Nervous System (CNS)
brain & spinal cord; integration occurs; main integration center; control center of the body; controls voluntary & involuntary movements; controls secretion of glands; makes up 99% of nervous tissue in body
Peripheral Nervous System (PNS)
outside of brain & spinal cord; mainly consists of nerves–communication lines; cranial nerves (12 pairs) & spinal nerves (30 pairs); part of NS outside of CNS; makes up 1% of nervous tissue in body
Effectors
responding organs; 2 types of effectors–voluntary & involuntary
Nervous tissue consists of
neurons & glial cells
Neurons
excitable nerve cells that transmit electrical signals; functional cells of nervous system; carries signals around; longest cell in body
Glial cells (Neuroglia)
supporting cells to neurons; help neurons carry out their functions; don’t carry signals; cells can divide
Peripheral Nervous System - 2 Divisions
- afferent (sensory) division - consists of nerves carrying info TOWARD CNS
- efferent (motor) division - consists of nerves carrying info AWAY FROM CNS & towards organs
Efferent (motor) division - 2 systems
- somatic nervous system - voluntary NS; nerves from CNS to skeletal muscles
- autonomic nervous system - involuntary NS; nerves from CNS to smooth muscles, cardiac muscles & glands
Autonomic nervous system - 2 divisions
act on same effectors but produce opposite responses
- sympathetic division - fight or flight
- parasympathetic division - rest & digest
Enteric nervous system (ENS)
nervous system associated with the digestive tract
Characteristics of neurons (nervous tissue)
- Excitable - responds to stimulus
- longevity - can last your whole life
- amitotic - not able to divide; born w/a certain # & we don’t get anymore
- high metabolic rate - metabolism occurs rapidly; very active; uses lots of ATP; requires continuous flow of O2 & nutrients
Brain makes up about 2% of body mass but uses
about 20% of body’s oxygen
cell body
contains nucleus, cytoplasm, organelles; main part of neuron; contains DNA; protein synthesis happens w/in cell body
nissl bodies
rough endoplasmic reticulum of neurons; synthesize proteins; most active ER in our body; only located in cell body
processes or nerve fibers (def’n 2 types)
extensions of the cell body;
- dendrites
- axons
dendrites
short branches clustered close to cell body; not myelinated; multiple dendrites; carries signals TOWARDS cell body; receiving info
axons
generate & transmit nerve impulses AWAY from cell body; only 1 axon per neuron; long part of neuron
axon hillock
narrow region of cell body where axon begins
axon terminals
branched ends of the axons; release neurotransmitters
axolemma
plasma membrane of axon; specialized for conducting nerve impulses; carries action potentials
myelin sheath
lipid-proein insulation covering some axons; consists of layers & layers of insulation around axon in Schwann cell
nodes of ranvier
gaps in the myelin sheath; exposed axolemma
Structures of a neuron
- cell body
- nissl bodies
- processes or nerve fibers
- axon hillock
- axon terminals
- axolemma
- myelin sheath
- nodes of ranvier
3 Structural Classification of neurons (based on # of processes)
- multipolar neuron
- bipolar neuron
- unipolar neuron
multipolar neuron
contains 3 or more processes; major neuron class in CNS; most common; lots of dendrites & 1 axon; 99%; motor neurons & CNS neurons
bipolar neuron
contains 2 processes; receptor cells in special sense organs; 1 dendrite & 1 axon; found in special sense organs; (ex. eye, ear, smell–designed for sensations)
unipolar neuron
contains 1 process; found mainly in the PNS; no dendrites & 1 axon; found in most sensory neurons; ex. pain sensors, touch sensors
multipolar interneurons
most abundant; in brain
Functional classification of neurons (describes direction they carry info)
- sensory or afferent neurons - carry impulses from sensory receptors TOWARD CNS
- motor or efferent neurons - carry impulses AWAY from CNS to effector organs
- interneurons - neurons between motor & sensory neurons, unually found in CNS; most abundant; responsible for integration (processing info)
Glial cells in the CNS:
- astrocytes - in brain; 10x more glial cells than neurons
- microglial cells
- ependymal cells
- oligodendrocytes
Glial cells in the PNS:
- satellite cells
2. Schwann cells
astrocytes
many processes, cover neurons, synapses, capillaries; most abundant;
function: physical support & ensures O2 & nutrients get to neurons; CNS
microglial cells
processes monitor health of neuron; function - protects nervous system from infection; CNS
ependymal cells
line central cavities of brain & spinal cord;
function: form barrier from cerebrospinal fluid from actual nervous tissue; CNS
oligodendrocytes
processes wrap around axons,
function: produces myelin sheath; CNS
satellite cells
surround neuron cell bodies within ganglia;
function: not sure what it does but thinks it regulates fluid outside of cell & inside cell & may be protective cell; PNS
Schwann cells
surround & form myelin sheath around axons; act like insulation; insulate axolemma so no cross signals between neurons; help in maintaining structure of axon; PNS:
function: myelinates axons
only axons can be myelinated
most axons are myelinated
nuclei
clusters of cell bodies in CNS
ganglia
clusters of cell bodies in PNS
tracts
bundles of neuron processes in CNS; bundles of axons
nerves
bundles of neuron processes in PNS; bundles of axons
myelinate
axon covered by Schwann cell
white matter
regions of the CNS composed mainly of myelinated axons (communication lines); brain-most white matter on inside of brain; spinal cord-most white matter on outside of brain
gray matter
regions of the CNS composed mainly of cell bodies & unmyelinated axons; brain-most gray matter on outside; spinal cord - most gray matter on inside
