AP - Nervous System Basics

Nervous System Function

detects changes affecting the body, makes decisions, stimulates muscles and glands to respond, and maintains homeostasis. Neurons are specialized to react to chemical and physical changes in their surroundings

2 types of neural tissue cell types

neurons and neuroglia

Neurons

react to changes

send nerve impulses for communication

Neuroglia

surround and support neurons

nourish neurons

send and receive messages

help maintain blood-brain barrier

2 main divisions of the nervous system

Central Nervous System (CNS) and Peripheral Nervous System (PNS)

Central Nervous System

Brain and Spinal Cord

Peripheral Nervous System

connects CNS to other body parts. Includes Cranial nerves and Spinal nerves

Sensory Function of the Nervous System

Nervous system receives information from the environment. The sensory receptors gather information by detecting changes inside and outside the body. This information is relayed to the CNS to be processed.

Integrative Function of the Nervous System

The NS coordinated sensory info to coordinate sensations, memories, and thoughts. The NS makes decisions based on the body’s response to changes.

Motor Function of the Nervous System

Decisions are acted upon. Impulses are carried to effectors (muscles and glands). The motor part of the PNS is broken into two parts: somatic and autonomic.

Somatic Nervous System

transmits voluntary instructions to skeletal muscles = contraction

Autonomic Nervous System

transmits involuntary instructions from the CNS to smooth muscle, cardiac muscle, and glands.

parts of a neuron

cell body, dendrites, and axon

cell body

contains nucleus, cytoplasm, and organelles just like other cells throughout the body.

dendites

branched, receptive surface

a neuron may have many

Axon

each neuron has one

transmits impulses and releases neurotransmitters to other effector

Axon Hillock

a cone-shaped thickening as the axon arises from the cell body

Axon Terminal

specialized, fine extensions near the end of the axon

Synaptic Knob'

Rounded end of an axon terminal. This lies close to the receptive surface of another cell - separated from the receptive surface only by a small space called the synaptic cleft.

Neuroglia

provide structural support for neurons

aid in specialization of cells in embryo

aid in formation of synapses

Ependymal Cells

line central canal of spinal cord and ventricles of brain. Associated with choroid plexuses and help regulate the composition of CSF

Oligodendrocytes

myelinates CNS axons, which increases speed of conduction of an impulse. Also provides structural suport

Microglia

Phagocytic cell

Removes excess ions and neurotransmitters.

Provides structural support

Astrocytes

connect neurons to blood vessels

provides neurons with nutrients

forms scar tissue following traumatic brain injury

regulates ion concentrations

Schwann Cells

myelinates PNS axons, which increases speed of conduction of an impulse

Satellite Cells

support clusters of neuron cell bodies

Nodes of Ranvier

gaps in the myelin sheath

Synapse

site at which a neuron transmits a nerve impulse to another neuron, muscle, or gland

Presynaptic neuron

sends the impulse

Postsynaptic neuron

receives the impulse

Synaptic Transmission

impulse travels down axon

Synaptic knob - influx of Ca2+ ions

Release of neurotransmitter from synaptic vesicles

The neurotransmitter exerts either inhibitory or excitatory effect on postsynaptic neuron depending on the receptor

Acetylcholine

stimulates skeletal muscle contraction

Norepinephrine

CNS - creates a sense of well-being

PNS - excite or inhibit the autonomic NS actions

Neurotransmitters are produced where

Rough ER or cytoplasm

Saltatory conduction

myelinated axons allow the impulse to ‘jump’ from node to node

What diameter of axons transmit faster

thicker

Sympathetic NS

fight or flight

Parasympathetic NS

rest and digest

Preganglionic fiber

neuron cell bodies are in CNS

Axons of preganglionic neurons

Postganglionic fiber

neuron cell bodies are in ganglia

axons of postganglionic neuron extend to visceral effector

Iris of eye response to sympathetic stimulation

dilation

Iris of eye response to parasympathetic stimulation

constriction

tear gland response to sympathetic stimulation

slightly increased secretion

tear gland response to parasympathetic stimulation

greatly increased secretion

muscle of intestinal wall response to sympathetic stimulation

decreased peristaltic action

muscle of intestinal wall response to parasympathetic stimulation

increased peristaltic action

muscle of internal anal sphincter response to sympathetic stimulation

contraction

muscle of internal anal sphincter response to parasympathetic stimulation

relaxation

salivary glands response to sympathetic stimulation

reduced secretion

salivary glands response to parasympathetic stimulation

greatly increased secretion

muscle in walls of bronchioles response to sympathetic stimulation

dialation

muscle in walls of bronchioles response to parasympathetic stimulation

constriction

muscle in walls of heart response to sympathetic stimulation

increased contraction rate

muscle in walls of heart response to parasympathetic stimulation

decreased contraction rate

muscle of bladder wall response to sympathetic stimulation

relaxation

muscle of bladder wall response to parasympathetic stimulation

contraction