Nervous system part I (1-27)

The nervous system

contains all neural tissue in the body and is comprised of

two different cell types

Neurons

cells that send and receive signals

Neuroglia

cells that support and protect neurons

Central nervous system (CNS)

contains the brain, brain stem, and spinal cord

Peripheral nervous system (PNS

delivers sensory information to the

CNS; transmits motor information from the CNS

Cell body

contains the perikaryon (cytoplasm) and nucleus

Dendrites

receive information from other neurons

Axon

carries electrical signal (action potential) towards target

Telodendria

extensions of the axons that end in synaptic

terminals

the synapse

where the action potential is converted into a chemical signal

The most important neuroglia

involved with myelination

Myelination

increases the velocity of an action potential

Oligodendrocytes

myelinate axons of the CNS

Schwann cells

myelinate axons of the PNS

Without myelin

the action potential would not travel quick enough from

one side of a neuron to the other side of the neuron, leading to a loss of

signal, overall

Action potential

the electrical propagation through a neuron in order to initiate a

response

Action potentials use factor (1) to work

Permeability

Action potentials use factor (2) to work

Electrochemical gradient

Action potentials use channel (1) to work

Sodium voltage gated ion channel

Action potentials use channel (2) to work

Potassium voltage gated ion channel

Depolarization

making the membrane potential less negative

Polarization

making the membrane potential more negative

At rest, the membrane of a neuron

is not very permeable to sodium, and slightly more permeable to potassium

When an electrical stimulation causes a threshold to be reached

first sodium voltage gated channels open, allowing an influx of sodium

After the peak of an action potential

sodium voltage gated channels inactivate and then potassium voltage gated channels open, causing a release of potassium

After a short afterhyperpolarization

the resting potential re-establishes

The absolute refractory period

an amount of time in which under no circumstances another action potential can be triggered

The relative refractory period

an amount of time in which an increased stimulus can trigger an action potential

If the threshold is reached

an action potential has to occur

If the threshold is not reached

an action potential never occurs

saltatory propagation

Propagation along a myelinated nerve

Saltatory propagation

the velocity of the action potential is quicker in myelinated segments, with restoration and slowing of the action potential in unmyelinated segments called the Nodes of Ranvier

When the action potential reaches a synapse

the electrical signal is changed into a chemical signal with the help of vesicular transport. Chemicals are used in the synaptic cleft to introduce the desired effect on the target tissue

Brain

contains 97% of the body’s neural tissue in the adult; exerts

centralized control of the other organs in the human body

Spinal cord

continuation of neural tissue off of the medulla oblongata; transmits information to and from the brain; independently responsible for numerous reflexes

Frontal lobe

involves the ability to recognize future consequences resulting from current actions and helps with the determination of similarities and differences between things or events

Temporal lobe

involves the retention of visual memories, the processing of sensory input, the comprehension of language, emotion, and the storage of new memories

Parietal lobe

helps integrate sensory information from various parts of the body; involved with the knowledge of numbers and their relations

Occipital lobe

primarily involved with processing visual information

Precentral gyrus

directs voluntary movement (primary somatic motor area)

Postcentral gyrus

receives somatic sensory information (senses- touch)

Meninges

membranes that surround the central nervous system

Dura mater

thick membrane and outermost of the meninges

Arachnoid mater

middle, web-like meningeal layer

Pia mater

the innermost and delicate meningeal layer; clings on to the brain and spinal cord

The ventricles of the brain

create and help transport cerebrospinal fluid (CSF)

Cerebrospinal fluid

clear, colorless, bodily fluid that helps protect the brain and spinal cord mechanically and chemically; found in the subarachnoid space (between pia mater and arachnoid mater)

Arachnoid granulations

projections of arachnoid mater that allow cerebrospinal fluid to enter the dural venous sinuses

Dural venous sinus

channel found between layers of the dura mater that receive blood from the veins of the brain and cerebrospinal fluid from the subarachnoid space; empty into the internal jugular veins

Pituitary gland

Endocrine gland responsible for interfacing the nervous system and the endocrine system

Diencephalon: thalamus

relay and processing centers for sensory information

diencephalon: hypothalamus

centers for controlling emotions, autnomic functions, and hormone production

midbrain

processing of visual and auditory data, generation of reflexive somatic motor responses, and maintenance of consciousness

pons

relays sensory information to cerebellum and thalamus, subconscious somatic and visceral motor centers, fine-tunes and smoothes breathing pattern

medulla oblongata

relays sensory information to thalamus and to other portions of the brain stem, autonomic centers for regulation of visceral function (cardiovascular, respiratory, and digestive system activities).

The spinal cord

begins past the medulla oblongata and tapers at the conus medullaris (L1 or L2)

Cauda equina

bundle of spinal nerves that continue off of the conus medullaris

Filum terminale

modification of pia mater that attaches the conus medullaris to the coccyx

The spinal cord and associated structures send off

8 cervical spinal nerve pairs
12 thoracic spinal nerve pairs
5 lumbar nerve pairs
5 sacral nerve pairs
1 coccygeal nerve pair

Cranial nerves

those that are connected to the brain

Spinal nerves

those that are connected to the spinal cord

Afferent nerves

those that carry sensory information to the CNS

Efferent nerves

those that carry motor information from the CNS

Autonomic nervous system: Sympathetic division

generally, causes stimulatory (fight or flight) effects on the body

Autonomic nervous system: Parasympathetic division

generally, causes relaxing (rest and digest) effects on the body

cerebrum

conscious thought processes, intellectual functions
memory storage and processing
conscious and subconscious regulation of skeletal muscle contractions

cerebellum

coordinates complex somatic motor patterns
adjusts output of other somatic motor centers in brain and spinal cord