Structure and organization, functions, neurons and neuroglial cells

what is the nervous system

the master controlling and communicating system of the body

cells in the nervous system communicate via

electrical and chemical signals

rapid and specific

usually cause almost immediate responses

functions of the nervous system

sensory input

integration

motor output

sensory input

info gathered by sensory receptors about internal and external changes

integration

processing and interpretation of sensory input

motor output

activation of effector organs (muscles and glands) produces a response

Organization of the nervous system - two major structural divisions

Central Nervous System (CNS)

Peripheral Nervous System (PNS)

The central nervous system includes

brain and spinal cord

functions of the CNS

integration center - it receives sensory information, interprets it, and makes decisions

Additional structures of the CNS

nuclei

tracts

gray matter

white matter

nuclei in CNS

clusters of neuron cell bodies in the CNS

tracts in CNS

bundles of CNS axons

Gray matter in CNS

neuron cell bodies + unmyelinated fibers

white matter in CNS

myelinated axons

the peripheral nervous system includes

all nerves outside the CNS

cranial nerves and spinal nerves

ganglia

function of the PNS

carries sensory input to the CNS and motor output from the CNS

additional structure in PNS

ganglia

nerves

ganglia in PNS

neuron cell bodies

Nerves in PNS

bundles of axons

Functional division of the nervous system

the PNS is split into sensory and motor divisions

Sensory (Afferent) Division

carries sensory input to the CNS

Components of the Sensory division

touch, pain, temperature, proprioception

Special senses

vision, hearing, taste, smell, equilibrium

Motor (Efferent) Division

carries motor output from CNS → effector organs (muscles & glands)

Motor division has two major branches: Somatic Nervous System and Autonomic Nervous System

Motor Division branch 1: Somatic Nervous System (SNS)

Voluntary control

effector: skeletal muscle

Function of the SNS

conducts impulses from CNS to skeletal muscles

allows voluntary movement

Motor division branch 2: Autonomic Nervous System (ANS)

involuntary; maintains homeostasis

effectors: smooth muscle, cardiac muscle, glands

splits into sympathetic, parasympathetic, and enteric divisions

sympathetic nervous system

fight or flight

increases heart rate

dilates airways

mobilizes energy

parasympathetic nervous system

rest and digest

slows heart rate

stimulates digestion

promotes maintenance activities

enteric nervous system

brain of the gut

controls GI motility and secretion

functions independently but communicates with sympathetic and parasympathetic systems

cellular components of the nervous system

neurons and neuroglia

neurons

functional cells

key parts:

• cell body

• dendrites

• axon

• axon terminals

dendrites

receive signals

axon

sends action potentials

axon terminals

release neurotransmitters

CNS Neuroglia

astrocytes

microglia

ependymal cells

oligodendrocytes

astrocytes

support neurons, regulate environment

microglia

immune cells, phagocytic

ependymal cells

make and circulate cerebrospinal fluid (CSF)

oligodendrocytes

form CNS myelin sheaths

PNS glial cells

schwann cells

satellite cells

schwann cells

form myelin in PNS

satellite cells

support neuron cell bodies in ganglia

Summary CNS

receives sensory input, sends motor output

Summary PNS

Sensory Division (somatic + special senses) → CNS
Motor Division:

• Somatic NS → skeletal muscle

• Autonomic NS

  • Sympathetic → smooth/cardiac muscle & glands

  • Parasympathetic → smooth/cardiac muscle & glands

  • Enteric → GI tract