Anatomy and Physiology Chapter 12 Nervous tissue

Functions of the Nervous system

Sensory Function, Integrative function, Motor Function

Sensory Function

Detect internal and external stimuli

Integrative function

Analyzes and stores sensory information.

Motor Function

Response that is appropriate for a stimulus

In CNS, Sensory=

Afferent

In CNS, Motor=

Efferent

Central Nervous System

CNS, Brain and spinal cord

Peripheral Nervous System

PNS, Cranial nerves and spinal nerves. Connect CNS to muscles, glands and sensory receptors.

Nuclei

CNS, Group of cell bodies

Ganglia

PNS, Group of cell bodies

Tract

CNS, Group of axons

Nerve

PNS, Group of axons

Somatic Nervous System

SNS, Sensory and motor. Connects to skeletal muscle (Voluntary).

Autonomic Nervous System

ANS, Sensory and motor. Connects to smooth and cardiac muscle as well as glands (Involuntary). Parasympathetic and sympathetic.

Sympathetic

Fight or flight

Parasympathetic

Rest and digest. SLUDD

SLUDD

Salvation, lacrimation, urination, digestion, deification

Entric Nervous System

ENS, Plexuses with in intestines. "Brains of the gut".

Cells of the nervous system

Neurons and neuroglia

Neurons

Generates action potential and processes electrical excitability.

When a neuron is damaged

You can't get it back

Parts of neuron

Cell body, axon, dendrites

Parts of the Cell body

Nissl Bodies and neurofibrils

Nissl bodies

Protein synthesis

Neurofibrils

Gives cell body structural support

Parts of the axon

Axon hillock, initial segment, axon collateral, axon terminals, synaptic end bulb. (Look at handmade flash cards)

Classification of a neuron

Structural and function

Neuron structure

Multipolar, bipolar, unipolar(Look at handmade flash card)

Unipolar

Sensory. Begins as a bipolar in embryo, but then axon and dendrite fuse together into a single process that divides into 2 branches at the cell body

Neuron Function

Sensory , motor, association

Multipolar

Motor

Bipolar

Retina

Neuroglia CNS

Astrocytes, Oligodendrocytes, microglia, ependymal cells.

Astrocytes

Blood brain barrier

Ogliodendrocytes

Myelin sheath

Microglia

Pac-man cells, eat up debris

Ependymal cells

Cerebral spinal fluid

Neuroglia of PNS

Schwann cells, Satellite cells

Schwann cells

Myelin sheath

Satellite Cells

Structural support

Neuroglia

Take care of neurons, can reproduce and can be fixed, take over when neurons are damaged.

Myelin Sheath

Multi-layered lipoid protein sheath that insulates axons and increases speed of nerve impulse

Nodes of Ranvier

Spaces between myelin sheath (Look at handmade flash cards)

Multiple Sclerosis (MS)

Losing myelin Sheath on axon, affects brain and spinal cord.

Ion channels

When open allow for passage of certain ions down electrochemical gradient, creates an electric current

Cations

Positive Ions that move towards a negatively charged area

Anions

Negative Ions that move towards a positively charged area. Most cannot leave cell because they are too big.

Types of Channels

Leakage, Ligand-gated, Mechanically-gated, Voltage-gated

Leakage gated

Opens and closes randomly (rest)

Ligand Gated

Chemical (Graded)

Mechanically gated

Physical distortion (Graded)

Voltage gated

Change in membrane potential (Action)

Resting membrane potential

Electrical voltage difference across the membrane at rest. Negative ions along inside of cell and positive ions along outside of cell.

Potential energy difference at rest

-70 mV which tells us that the neg. inside the cell is stronger with respect to the outside of the cell. The number 70 tells us the magnitude.

Graded potentials

Small change in a charge from resting potential of -70 mV. Localized, Graded, Decremental, mechanically gated and ligand gated.

Hyperpolarization

Membrane has become more negative (-70 becomes a larger negative number)

Depolarization

Membrane has become more positive and towards threshold

Localized

Generating a change locally

(Graded) Small stimulus=

Small response

Where do graded potentials occur most often?

Dendrites and cell body

Action potential/impulse

Sequence of events rapidly occurring and take place in 2 phases

Generation of an action potential

1) Impulse, 2)Depolarization, #)Repolarization, $)Hyperpolarization, 5) Voltage-gated channels

K+ Voltage gated channels

Closed or Open. Open and close very slowly (Look at flashcards)

Na+ Voltage gated channels

Closed Open Inactive (Look at flashcards)

Action potential starts when-

Threshold is hit

All or none law

Depolarization reaches certain threshold, and voltage gated channels open. Action potential occurs and the size and amplitude always stay the same

Refractory Period 2 states

Absolute and Relative

Absolute refractory period

Cannot get another action potential to occur (look at flashcards)

Relative refractory period

Can get an action potential, but is very hard (Look at flashcards)

Graded potentials do not have-

Refractory Period

Impulse conduction

Continuous and saltatory

Continuous impulse conduction

Depolarization and repolarization of each adjacent segment of cell membrane of neuron. Unmyelinated axons and fibers. (Flash card)

Saltatory impulse conduction

1) Ionic current, 2)Depolarize membrane, sodium channels open, impulse jumps from one node to another. (Nodes of ranvier) (Flash card)

Signal transmissions

junction between neuron-neuron or neuron-effector

Electrical signal transmission

Action potential conducted directly between adjacent cells through gap junctions

Chemical signal transmission

Specialized for release and reception of chemicals (Neurotransmitters)