Human Biology: The Nervous System

The 2 parts of the Nervous System

CNS - the Central Nervous System, which is the brain and spinal cord

PNS - The Peripheral Nervous System, which is made up of 12 pairs of cranial nerves and 31 pairs of spinal nerves

The three types of neurons

Sensory Neurons

Interneurons

Motor Neurons

Functions of sensory neurons

Sensory neurons takes information from peripheral receptors and relay it to the CNS. A very long axon, often covered with a lipid called myelin carries nerve signals from the dendrites associated with a receptor to the CNS.

Functions of Interneurons

Interneurons receive sensory input from sensory neurons and also information from other neurons. They are all inside the CNS.

Functions of Motor neurons

Motor neurons carry nervous impulses to effector muscles, glands and organs, which carry out the responses, both external and internal.

The parts of a neuron

Cell body

Dendrites

Axon

Axon terminal

Functions of a cell body of a neuron

It has the nucleus and other organelles

Functions of dendrites

It picks up information from receptors of other neurons

Functions of axons

It is a bunch of nerve fibers that make up a nerve

It transmits signals to other neurons or effector cells

Functions of axon terminals

Creates the synapse between neurons and effectors

Function of myelin on an axon

It insulates the axon

The cell that deposits the myelin in the CNS

A supportive neuroglial cell called an Oligiodendrocytes

A nervous synapse

A "connection" between two neurons.

When the axon terminal of one meets the dendrites of another.

Gray matter

Regions within the central nercous system composed mainly of nerve cells bodies and dendrites.

The outer 3-4 mm of the brain.

The most highly evolved nervous tissue.

Where nervous synapses occur.

Allows us to think, speak, remember, and contract muscles.

Gray matter is made of this

Unmyelinated axons, cell bodies, dendrites and neuroglial cells

White matter is made of this

Myelinated axons within the CNS

What neuroglial cells do

They support and protect

A certain one, Oligiodendrocytes, deposit myelin

They vastly outnumber neurons

They have mitosis and the ability to divide

A Node of Ranvier

An unmyelinated region on a myelinated axon of a nerve cell, where nerve signals are regenerated.

A gap between oligiodendrocytes.

How a resting neuron's cell membrane is similar to a charged battery

The cell membrane and the distribution of charge ions on either side of it create a resting membrane potential, similar to a battery.

Like batteries, an energy source created by separating positively charge ions across a membrane from negatively charged ions, the potential energy in the cell membrane can be used to perform work.

See Figure 28.3 in textbook

How a nerve signal or action potential is conducted

An action potential is another name for a nerve impulse.

Here, the energy stored in the "battery" of the resting membrane potential of the cell membrane and put to work as a nerve signal is conducted.

This begins when there is a sufficient stimulus that activates the neuron at the axon hillock where the axon meets the cell body of the neuron. The action potential is then spread one way down the axon to the axon terminal, which causes release by exocytosis of neurotransmitters.

See figure 28.4

What salutatory conduction is

Allows action potentials to leap from Node of Ranvier to Node of Ranvier

What happens at the axon terminal when an action potential reaches there

The neurotransmitters are stored in synaptic vessicles in the axon terminal. When the action potential reaches the axon terminal, ion channels for calcium open and calcium ions, Ca++, enter and trigger the release of the neurotransmitter. The released neurotransmitter diffuse across the tiny synaptic cleft to the next membrane of a dendrite, cell body or effector.

Synaptic integration

It is neurons adding up all the excitatory signals and compare them to all the inhibitory signals it receives.

See figure 28.6 and 28.7

What happens during an action potential

Membrane voltage changes and a nerve signal is transmitted along an axon.

What nerves are

They are bundles of myelinated axons from sensory and motor neurons.

What the cerebral cortex is, where it is located and is it made of gray matter

It is on the surface of the cerebrum and it is made of gray matter

Where synapses between neurons occur

They occur in gray matter

Where do action potentials start in the CNS

They start in the axon hillock in gray matter

What the resting membrane potential usually is

-70 mV

What happens when the action potential reaches the axon terminal of a neuron

Voltage gated channels for Ca++ open, Ca++ enters the ICF and causes release of neurotransmitters by exocytosis

What cerebrospinal fluid is

Blood-derived fluid that surrounds, nourishes, and cushions the brain and spinal cord.

Where cerebrospinal fluid is formed

From neuroglial cells filtering capillaries in the roof of the brain ventricles

Where cerebrospinal fluid circulates

In the space between the pia mater and arachnoid meninges lining the CNS

Where cerebrospinal fluid drains when it needs replenished

The venous circulation

What is found in the dorsal root

Ganglion or cell bodies of sensory neurons

What is found in the ventral root

Axons of motor neurons of 31 pairs of spinal nerves

The three parts of the brainstem

The midbrain

The medulla oblongata

The pons

The functions of the medulla oblongata

Pacemaker for breathing-DRG, cell bodies of 4 pairs of cranial nerves, including those from the vagus nerve which controls the parasympathethic nervous system, cardiovascular centers for heart rate and blood pressure

What happens in the decussation in the medulla oblongata

Motor neuron fibers cross over to the other side of the body here

Function of the pons

Located of respiratory centers that makes sure one is breathing deep enough for the pace of breathing set in the medulla oblongata, four pairs of cranial nerves have their cell bodies there, bridge between the upper brain and the rest of the nervous system

What neurotransmitter is produced by the substantia nigra of the midbrain

Dopamine, important for the inhibitory part of muscle tone - a lesion here could cause Parkinsons's disease

Function of the cerebellum

It coordinates skeletal muscles so you do not fall or stumble

Location of the cerebellum

Below (or "inferior") to the posterior part of the cerebrum (the occipital lobe) and behind (or "posterior") to the brainstem.

Function and location of both Broca's area in the cerebrum

Word formation

Function of Wernickes area

Word planning on what to say

Major function of thalamus

Relay center for most sensory impulses to the correct location in the cerebral cortex

Function of the hypothalamus

Controls autonomic nervous system, centers for sleep, body temperature, salt/water balance in blood, sex, eating, links endocrine system to the nervous system, controls the anterior and posterior pituitary glands, sleep, satiety centers

Where short term memory is stored

Pre frontal area behind forehead

Where long term memory is stored

Long term memory is stored in bits of information through out the sensory association areas of the cortex of the cerebrum. The hippocamus acts as a bridge between the sensory association areas, where memories are stored, and the prefrontal area, where memories are used.

See figure 13.9

How many motor neurons in voluntary motor pathways of the somatic nervous system to skeletal muscles

2

How many motor neurons in the autonomic nervous system outside the CNS

2

How many pairs of cranial nerves there are

12