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
Describe the two different types of neurotransmitters
Excitatory neurotransmitters
* Usually cause an influx of sodium so that the
neurons will be depolarized (make inside of cell
more positive)
* Inhibitory neurotransmitters (no impulse transmitted)
* Cause entry of chloride ions which lead to
hyperpolarization (make inside of cell more
negative)
Give at least one example of excitatory neurotransmitters and inhibitory neurotransmitters each
excitatory NT: dopamine, serotonin
inhibitory NT: GABA
What are the four main parts of the brain and what are the structures under each part?
A. Cerebrum
(cerebral cortex)
* B. Diencephalon
* Thalamus
* Hypothalamus
* C. Brain Stem
* Midbrain
* Pons
* Medulla oblongata
* D. Cerebellum
List the five major functional regions/areas of the brain cortex and understand their functions. (smavh) (cerebrum cortex)
Sensory areas
* receive somatic sensory information from
different part of body
* Motor areas
* initiate/coordinate motor activity in muscles
* Auditory areas
* receive hearing information from ears
* Visual areas
* Receive visual information from eyes
* Higher functional areas (eg.
prefrontal cortex)
* solving the complex tasks
function of cerebrum
Controls conscious activities, intelligence, memory, language,
muscles.
function of cerebellum
Area of the brain responsible for coordination of movement, balance, posture
function of the brain stem
Consists of the medulla
oblongata, pons and midbrain
* Brain stem is responsible for
vital life functions such as
breathing, heartbeat, and
blood pressure
function of diencephalon
Relay station between brain stem and
cerebrum
* Thalamus - acts as a relay station for sensory
inputs to the cerebrum
* Hypothalamus - interface between the
nervous system and the endocrine system
Correctly label the following structure in a brain picture: cerebrum, cerebellum, brain stem, Pons, medulla oblongata, hypothalamus
How is CNS protected?
Brains and spinal cord are protected by Cranium (bones of brain) Vertebral column and Meninges
describe the three layers of meninges membrane.
Three layers of
membrane (surface to
depth)
covers brain and spinal cord
* Dura mater (doublelayered external
covering below the bone
of skull)
* Arachnoid layer
(middle Web-like layer)
* Pia mater: Internal layer
(blue)
What is the composition of CSF?
similar to blood
plasma
Where does CSF circulate?
in brain ventricles and spinal
cavity in arachnoid space (space below the
arachnoid layer)
What are the functions of CSF?
The primary function of CSF is to cushion the brain
within the skull and serve as a shock absorber for the
central nervous system
* CSF also circulates nutrients and chemicals, removes
waste products from the brain and spinal cord
The number, name and function of each of the 12 cranial nerve
I olfactory- smell
II optic -sight
III oculomotor -moves eye, pupil
IV trochlear- moves eye
V trigeminal -face sensation
VI abducens- moves eye
VII facial -moves face, salivate
VIII vestibulocochlear- hearing, balance
IX glossopharyngeal -tastes, swallow
X vagus -heart rate, digestion
XI accessory -moves head
XII hypoglossal -moves tongue
Describe the structure of a spinal cord
The spinal cord consists of well-organized nerve fibres running in
tracts.
* Its uniform structure extends throughout its entire length, with outer
white matter surrounding the central grey matter.
* Additionally, it is enveloped by the meninges and surrounded by
cerebrospinal fluid (CSF), which also flows within the central canal.
In a transverse section, the grey matter
displays a distinctive butterfly shape.
The ventral horns stand out, housing the
cell bodies of the large motor neurons,
whereas the dorsal horns house the cell
bodies of the comparatively smaller
sensory neurons.
The white matter contains a greater
proportion of myelin and consists of
ascending tracts of sensory fibres and
descending motor tracts
Reflex
- A reflex is an involuntary and nearly instantaneous movement
(response) to a stimulus (suddenly pulling back your finger from
hot object) - A reflex is made possible by neural pathways called reflex arcs
which are organized at spinal cord level without involvement of
brain - Reflex protects the body against potential damage by its fast
response, due to the short neuronal circuit involved
What are the neuronal circuit involved in reflex (what is a reflex arc)?
Receptor (nerve endings in the skin)
* Sensory neuron
* Spinal cord
* Motor neuron
* Effector (muscles)
