Chapter 14 The Nervous System

Central nervous system

Consists of the brain and spinal cord

Peripheral nervous system

The sensory (afferent) and motor (efferent) neurons that connect the CNS to the rest of the body, including all cranial and spinal nerves and ganglia.

Ganglia

Collections of nerve cell bodies

Afferent

Towards

Efferent

Away from

Nerve

A bundle of axons of neurons located in the PNS

Sensory neuron

A neuron that carries nerve signals from a sensory receptor towards the spinal cord and brain (afferent neurons)

Interneuron

A neuron located only within the CNS that integrates incoming sensory information and determines whether the signal should be pass to a motor neuron and effector.

Motor neuron

A neuron that carries nerve impulses away from the brain and spinal cord (efferent neuron, takes messages to effectors)

Effector

An organ that performs a response; either cardiac muscle, skeletal muscle, smooth muscle, or glands.

Neuron

Cell that transmits nerve impulses via action potentials (electrical changes)

Neuroglia

All other cells in the nervous system, which support and nourish neurons

Cell body

Part of a neuron that contains the nucleus and most other organelles of the cell.

Dendrites

Short extensions off the cell body that receive signals from sensory receptors or other neurons.

Axon

Portion of a neuron that conducts nerve impulses (action potentials)

Schwann cells

Form myelin sheath in PNS

Node of Ranvier

Space between Schwann cells, and thus between myelin.

Saltatory conduction

Conduction of an impulse from space to space between cells that produce myelin (Schwann cells).

Resting potential

The potential energy of a neuron at rest, when it is not conducting a nerve impulse.

Action potential

A rapid electrical change in the axon that allows a signal to be sent; also called a nerve impulse. Instead of being more negative inside the cell membrane, and more positive outside, the charges flip to being more positive inside the cell and more negative outside the cell. This flip travels like a wave down the axon.

Depolarization

When sodium gates open in an axon, and positively charged sodium rushes inside causing it to become more positive inside the cell than outside.

Repolarization

Sodium gates close, and potassium gates open in an axon, letting out the positive charge that had rushed in and returning the inside charge of the axon back to being more negative than it is outside.

Sodium-potassium pump

A carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell. It resets the arrangement of ions after an action potential wave passes.

Synapse

A small gap between the neuron sending a signal and the neuron receiving a signal, preventing any neuron from touching another neuron.

Neurotransmitter

A chemical messenger used by a neuron to transmit an impulse across a synapse to another cell, because they are not touching.

Axon terminals

The ends of an axon in which neurotransmitter is stored.

Gray matter

Tissue of the nervous system that contains nonmyelinated axons and cell bodies.

White matter

Tissue of the nervous system that contains myelinated axons and is thus white in color.

Cerebrum

Largest portion of the brain that is divided into the frontal, temporal, parietal, occipital, and insular lobes. Has many gyri and sulci.

Cerebral cortex

The thin, outer layer of the cerebrum made of gray matter, in which much of human thought, planning, perception, and consciousness takes place

Primary motor area

Voluntary control of skeletal muscles

Primary somatosensory area

Receives sensory information from skeletal muscle and skin

Association areas

Multiple areas of the cerebrum where information is integrated/processed.

Processing centers

Areas of the cerebrum that perform higher analytical functions including Wernicke's and Broca's areas, both involved in speech.

Diencephalon

The deepest, most central part of the brain that controls many involuntary functions and also transports signals to the correct location of the cerebrum.

Hypothalamus

Helps maintain homeostasis (hunger, sleep, thirst, body temperature, water balance) and controls the pituitary gland.

Thalamus

Two masses of gray matter that receive all sensory input except smell and direct it to the appropriate location of the cerebrum; also involved in memory and emotion.

Pineal gland

Secretes melatonin and regulates circadian rhythms

Cerebellum

Receives and integrates sensory information of the eyes, ears, joints, and muscles about the position of the body in space.

Brainstem

Connects to the spinal cord and relays information into the thalamus and cerebellum, also contains reflexes for regulating breathing, heartbeat, and blood pressure as well as consciousness.

Reticular formation

A functional neural system of the brain responsible for maintaining consciousness when we are awake, and allows unconsciousness during sleep.

Limbic system

A functional neural system of the brain associated with emotions and drives.

Learning

What happens when we recall and use past memories

Memory

The ability to hold a thought or to recall past memories.

Short-term memory

The retention of information for only a few minutes.

Long-term memory

Retention of information for more than a few minutes.

Skill memory

Performing skilled motor activities without conscious thought (e.g. riding a bike, typing)

Somatic nervous system

Voluntary part of the brain that serves the skeletal muscles and tendons.

Autonomic nervous system

Regulates the activity of involuntary muscles (cardiac and smooth) and glands. Further divided into sympathetic and parasympathetic divisions.

Sympathetic division

Coordinates the body for the "fight or flight" response by speeding up metabolism, heart rate, and breathing while slowing down and regulating other functions.

Parasympathetic division

Counters the sympathetic system by bringing up a relaxed state by slowing down metabolism, heart rate, and breathing, and returning other functions to normal.

Alcohol

A depressant directly absorbed from the stomach and small intestine.

Nicotine

Stimulant derived from tobacco plant.