nervous system Flashcards
Describe the organization of the nervous system (or draw the organization chart of the nervous system)
Describe the three main functions of the nervous system.
- To receive information/stimuli from the external
and internal environment by sensory nerves - To analyse and integrate these stimuli from the
sensory pathway by Central Nervous System
(CNS
- Brain and spinal cord) - Initiate response of effector (such as muscle
contraction) by sending signal via motor
nerves
what is cns made up of and what does it do
Made up of brain and
spinal cord
what it does: Acts as body’s
control center
* Coordinates body’s
activities
* Nerve Impulses
travel through the
neurons in your body
to reach the brain
what is the PNS made up of
- Made up of all the nerves
that carry messages to and
from the CNS (transporters)
Divisions of PNS - Sensory
Sensory (afferent) division
Nerves carrying information to the CNS
* Somatic (skin, muscle, joints) sensory nerves
carry sensory inputs from skin, muscle, joints,
are involved in the voluntary control of body
movements
* Visceral sensory nerves carry
sensory impulses (usually pain or reflex
sensations) from the internal organs, glands,
and blood vessels to the central nervous
system.
Divisions of PNS - Motor
Motor (efferent) division:
Nerves carrying information FROM the CNS
Somatic Nervous System
- Voluntary
- Conducts impulses from CNS to skeletal muscles
Autonomic Nervous System (ANS)
- Involuntary
- Conducts impulses from CNS to cardiac muscles,
smooth muscles, and glands.
- ANS includes two divisions:
- Sympathetic Nervous System
- Parasympathetic Nervous System
Divisions of PNS - Autonomic
Sympathetic Nervous System: controls
body in times of stress, such as the
secretion of adrenal
* Parasympathetic Nervous System:
controls body in times of rest (such as
sleep)
* Sym and Parasym nervous system
usually have opposite effects on the
same organ to balance the activity of the
organ
Describe the difference between sensory and motor nervous system.
Give at least 6 examples of the functions of sympathetic and parasympathetic nervous system
1.para: constrict pupils, symp: dilate pupils (think to see better)
2.para: slow heartbeat , symp: increased heartbeat
3.para: contrict airways, symp: relaxed airway (think for more air for running)
4.para: stimulate activity of stomach, symp: inhibit activity of stomach
5.para: stimulate activity of intestine , symp: inhibit activity of intestine
6. para: contract bladder, symp: relax bladder (no time to pee)
Describe the structure of a neuron
Neurons are composed of
- One or more dendrons or dendrites, -
branch like tiny trees and carry nerve
impulses towards the cell body
- With large surface area to receive signals
to the cell body
- A cell body (containing the nucleus)
- An axon – carry the nerve impulse
away from the cell body
- single, long process in each neuron,
conduct signal away from cell body to
other neurons
What are the major glial cells in PNS and CNS that form myelin sheaths around the axons?
pns: schwann cells (look like swarma wrap)
cns: oligodendrocytes (little ball-o)
What is a node of Ranvier?
The gaps between adjacent glial cells is called Nodes of Ranvier.
why myelin can help to speed up the signal transduction through the axon?
- Myelin is an insulating layer, which helps to actually conduct
signals through the axon at a much faster speed than
unmyelinated axons
function of glia cells
support, nourish and
protect neurons like “glue”
what is the myelin sheath
Cell membrane of glial
cells tightly wrap around
the axon to form a
covering of axon called “Myelin Sheath” * Oligodendrocytes in CNS * Schwann cells in PNS
What are grey matter and white matter
gray matter: unmyelinated
axon terminals
* Dendrites
* Cell Bodies
white matter: Consists of
– Myelinated axons (myelin made up of fat-> white)
Action Potential
An action potential is the electrical signal that
allows nerve impulses to propagate along the axon of a neuron.
tells impulse to move)
The process of generating an action potential involves
several membrane mechanisms:
1) Resting Membrane Potential
2) Depolarization
3) Rising Phase
4) Repolarization
5) Hyperpolarization
what happens during resting membrane potential
Neurons have a resting membrane
potential, which means there is a voltage
difference across their cell membrane
when they are not actively sending
signals.
* At rest, the inside of the neuron is
negatively charged relative to the outside.
* This resting membrane potential is
typically around -70 millivolts (mV).
The voltage difference between the 2 sides of
cell membrane in a neuron is largely due to
distribution of different ions on the 2 sides of membrane. There are ion channels located at
the cell membrane
* Ions such as sodium, potassium flow through the ion channels
what happens during depolarization
- When a neuron receives a strong enough stimulus (e.g., from a
neighbouring neuron), it can cause a temporary increase in
permeability to sodium ions (Na+). - Sodium channels in the cell membrane open, allowing Na+ to
rush into the neuron. - This influx of positive charge causes the inside of the neuron to
become less negative, a state called depolarization. - Depolarisation leads to the excitation (activation) of the
neuron.
what happens during rising phase
The rapid influx of positively charged sodium
ions leads to a sharp rise in the membrane
potential, reversing the polarity of the neuron’s
membrane.
* The inside becomes positively charged relative
to the outside, creating the action potential
(AP).
* Depolarized/excited neurons generate the
electrical impulse, traveling along the axon.
* AP is mainly due to the flow of Na+ into the cell
what happens during repolarization
After reaching its peak (around +30 mV to +40 mV), the
voltage-gated sodium channels start to close, and
voltage-gated potassium channels begin to open.
* The efflux of potassium ions (K+) repolarizes the
membrane, bringing it back to its negative resting
potential.
what happens during hyperpolarization
In some neurons, the efflux of potassium ions can
briefly cause the membrane potential to become more
negative than the resting potential.
* This phase is called hyperpolarization, and it is usually
short-lived. (potassium channels close slowly, too many potassium ions flow out causing it to be more negative than its suppose to me)
How the signal is passed between two neurons
When an action potential reaches the
axon terminal
* Neurotransmitters (NT) are released
from axon terminal
* NTs are molecules generated by a neuron.
* The receptors on the dendrite of the next
neuron are stimulated by the NT,
* leading to the excitation of next neuron
* A new AP would be generated in the next
neuron
