Nervous System 1 Flashcards
CNS and PNS
Central nerve system and peripheral nervous system
- Nucleus/Nuclei
- Ganglion/Ganglea
- A group of neuron cell bodies in the CNS
- A group of neuron cell bodies in the PNS
- Tract
- Nerve
- Bundles of axons in the CNS
- Bundles of axons in the PNS
- nerve plexuses: a network of intersecting nerves
Functions of the Nervous System
It had 3 basic functions
Sensory Input: detects changes in internal and external environments
Integration: makes sense of those and decided on the proper motor response
Motor output: brings the response to an effector(body part)
- Somatic Nervous System
- Autonomic Nervous System
- Are in charge of voluntary and conscious controls
- controls skeletal muscle - Are in charge of involuntary control
- controls smooth and cardiac muscles and glands
Nervous tissue:
consists of two types of cells
- neurons: the functional cells of the nervous system that carry nerve impulses (known as action potential)
• neuroglia: the cells that support, nourish, and protect the neurons
The 4 characteristics of a Neuron
- excitability: neurons generate and conduct action potentials
- long lifespan: neurons can last a lifetime, as long as they are not damaged by disease or trauma.
- high metabolic rate: neurons require a continuous and abundant supply of oxygen and glucose
- lack of regeneration (with few exceptions)
Nervous tissue:
1. What carries impulses towards the cell?
2. What contains the nucleus of the neuron
3. What carries impulses away from the cell
4. Where does ap start
5. And where does it end
Word bank: axon hillock, axon, the cell body, axon terminal, dendrites
Ans key is on notes
Look at diagram
Strucally, neurons differ
By the number of processes extending from the cell, multipolar, bipolar or unipolar
Nervous tissue;
The 2 types:
Neuroglia
Are the e guardians of the brain
Don’t conduct impulses
Identify the location and function of each
- Oligodendrocytes
- Schwann cells
- CNS, Produce myelin sheaths around multiple segments of many axons
- PNS, Produce myelin sheaths around one segment of one axon
Read the rest on notes
Myelination
Both oligodendrocytes and Schwann cells wrap around an axon and form the myelin shealth
True or False
All axons are covered with myelin
False:
Not all axons are myelinated
Myelination info
In unmyelinated axons: nerve impulses travel continuously along the axons.
In myelinated axons: nerve impulses occur only at the gaps (nodes of Ranvier), where the axonal membrane is exposed.
• known as saltatory conduction: about 30 times faster
Multiple sclerosis (MS) is a disease in which the myelin sheaths are destroyed. What process does this interfere with and what would be the consequence?
When myelin sheaths are destroyed, this is known as demyelination.
With reduced or lack of myelin sheaths, saltatory conduction is affected.
This will result in a slowing down and even permanent cessation of nerve impulse conduction.
Neuron Commication:
Neurons “start a conversation” by changing its resting membrane potential (RMP).
There are two types of signals:
1. Graded potential
2. Action potential
Graded Potential
are short-lived and decay
• Hyperpolarization: membrane potential becomes more negative than the RMP.
• Depolarization: membrane potential becomes more positive than the RMP.
Graded potential can be
added (summated). The stronger the stimulus, the bigger the graded potential.
Action Potential
a form of communication that only occur in neural axons and muscle cells.
In neurons, they are referred to as a nerve impulses.
• Only occur when a neuron reaches a critical level called the threshold
These 2 words describe APs
All or none
Self propagating
All or none: They cannot be added together
Self propagating: won’t lose their strength and they have the same magnitude
APs have 4 stages
For each one, different voltage gates channels open or close to allow ions to flow:
Depolarization: Na enters the cell(VG-Na channels are open)
2) Repolarization: K+ leaves the cell (Na+ entry slows)- Vg Na are closed, Vg K+ are open
3) Hyperpolarization: K+ leaves the cell (Na+ entry stops)-Vg K+ are open
4) Resting state (baseline): Nat pumpedout and K+ pumped into the cell by Na+/K+ pump-both channels are closed
True or False
Depolarization in a neuron leads to an action potential
False
Refractory Period
Is a time where the neuron is resistant to additional stimulus
Refractory Period:
Types:
During absolute refractory period:
• VG-Na channels are either open or inactivated
• neurons cannot depolarize again and cannot generate another AP
During the relative refractory period:
• most VG-Na channels have closed, but K+ channels are still open
• neurons is a hyperpolarized state, and thus need a larger than normal stimulus to reach threshold again
True or False
Stronger stimulus generates a stronger action potential
False:
Action potential is all or none. All action potentials are alike and are independent of stimulus intensity.
A stronger stimulus
Generates a stronger graded potential by increasing the frequency of APs
