The Nervous System Flashcards
1- identify the two major subdivisions of the NS
Peripheral NS- extremities of the body
Central NS- centre of the body
1- what are the two major divisions of the peripheral NS?
Autonomic- self regulated actions of internal organs and glands
Somatic- voluntary actions
1- identify the two divisions of the autonomic NS
Sympathetic- arousing
Parasympathetic- calming
1- identify the two divisions of the somatic NS
Sensory input
Motor output (controls skeletal muscles)
1- what is the CNS comprised of?
Composed of- Brain and spinal cord
Contains- relay neurones (interneurons)
1- what is the PNS comprised of?
Composed of- cranial nerves, spinal nerves, peripheral nerves
Contains- sensory neurones, motor neurons
1- what is a neurone?
The basic functional unit of the NS
The NS has over 100 billion neurones in it
1- name as many structures of the neuron as you can
Dendrites
Nucleus
Axon
Axon terminal
Myelin sheath
Cell membrane
Cell body
Axon hillock
Ogliodendrocyte
Nodes of Ranvier
1- what are neuroglia?
The supporting cells of the NS
1- what is an Ogliodendrocyte?
A type of neuroglia
Main job is to support and insulate myelin on axons in the CNS
1- name the three other types of neuroglia and their functions
Astrocytes- help to form the blood-brain barrier
Microglia- remove bacteria and damaged tissue
Ependymal cells- secrete CSF
1- how do you differentiate between neurones in the PNS and the CNS?
PNS neurones- are myelinated by Schwann cells
CNS neurones- are myelinated by Ogliodendrocytes
2- outline the functions of the brain stem
The brain stem is the stalklike part of the brain that connects it to the spinal cord. It is part if the CNS
Overall function- regulates some bodily functions and sends messages between brain and the body
Functions of the brain stem:
It coordinates messages that regulate…
-balance
-blood pressure
-breathing
-facial sensations
-hearing
-swallowing
-heart rhythms
3- what are the meninges of the brain and spinal cord?
Three layers of membrane that protect the brain and spinal cord
Meninges separate them from their bing casing
3- name and describe the three meninges of the Brian and spinal cord
Pia mater-
Delicate inner matter
Highly vascular membrane that closely follows brain contours
Function is to physically separate neural tissue from blood vessels
Arachnoid-
Middle layer
Web-like structure filled with CSF that cushions the brain
All cerebral arteries and veins are located here
Dura mater-
Tough outer layer
Made of dense connective tissue
4- identify the origin of CSF, how is it made?
It is formed in the cerebrospinal ventricles
Ependymal cells create CSF, it is then secreted by the choroid plexus
It is constantly secreted, so is completely renewed 5 times in a day
4- what functions does CSF perform?
It has 5 main functions:
1- Support
Supports the weight of the brain and keeps it buoyant
2- Shock Absorber
Protects the brain from damage and head trauma
3- Homeostasis
Electrolytes maintain osmotic pressure
Maintains a stable temp
Waste products removed
4- Nutrition
Glucose, protein and lipids
5- Immune Function
Contains immunoglobulins
5- outline the process and stages of action potential generation (9 stages)
1- Stimulus is received
2- Stimulus changes voltage so that threshold is met
3- Voltage gates sodium channels open
4- Sodium moves into cell
5- Depolarisation- inside if cell gets more positive
6- Voltage change triggers opening of potassium channels
7- Potassium leaves the cell
8- Repolarisation- Inside of cell becomes more negative
9- Returns to resting membrane potential
5- outline how axonal conduction works in regards to neuronal structure
Action potentials are negatively charges electrical signals that travel down a neuron, this is how messages are sent
Messages start at the neuronal soma and need to travel to axon terminals
Neurons are wrapped in myelin- myelin is a conductor and assists the electrical messages along
5- outline the process of synaptic transmission
=the process by which one neurone communicated with another
Terminal boutons live on the axon terminals
Terminal boutons contain synaptic vesicles
Synaptic vesicles store synthesised neurotransmitters
1- Action potential arrives
2- Opens voltage gated calcium channels
3- Triggers the vesicles, they move to fuse with nerve membrane
4- Neurotransmitters diffuse across the synaptic cleft
5- Act in the receptors in the post synaptic neuron
Neurotransmitters affect the post synaptic neurone for as long as they exist in the synaptic cleft
Most neurotransmitters have an excitatory effect
5- outline the process of neuromuscular transmission
= Interaction between a neurone and a muscle
Acetylcholine (ACh) is the neurotransmitter responsible for neuromuscular transmission
1- Nerve impulses arrive at axon terminal
2- Triggers the opening of voltage gates calcium channels
3- Vesicles fuse with axon membrane
4- ACh released into the synapse
5- ACh acts in ACh receptors- they open
6- Sodium enters- if threshold is met then action potential is generated
5- differentiate between the two types of sensory neurons
Pseudo Unipolar- has one axon
Bipolar- has two completely independent axons that extend from the cell body
5- briefly describe the concept of resting membrane potential
RMP of a neurone is -70mV
A resting neurone has a voltage across its membrane, this is the RMP
It is determined by ion concentration gradients
In a resting neuron, there is resting potential gradients for sodium (Na+) and potassium (K+)
Ions move down their gradients via channels
This separates the charge that creates the resting potential
Membrane is more permeable to K+ than Na+
So resting potential is closer to the equilibrium potential of K+
6- how is sensory information conveyed to the CNS through activation of sensory receptors?
Tactile stimuli activate sensory receptors in the skin, muscles, joints etc
Axon of dorsal root ganglion neurone joins white matter in spinal cord
Axons terminate in the nuclei of the medulla
Axons communicate through synaptic transmission till it reaches the brain stem
Axons bundle in the brain stem
Axons then terminate in the thalamus to connect with the final neurone in its pathway
Final neurone projects it’s axons to the gurus in the cerebral cortex
In the gurus, somatosensory stimuli are processed
Appropriate physiological reaction is carried out
7- in the spinal cord, where is the white and grey matter?
Grey matter- creates a hornlike structure throughout the inside of the spinal cord
White matter- encases the grey matter to make up the surrounding sections
7- in the spinal cord, where is the central canal?
The CSF filled space that runs through the spinal cord
7- in the spinal cord, where is the dorsal and ventral horns and roots? What are they?
Two pairs of nerve roots that extend from each segment of the spinal cord
Ventral roots (anterior/front of the body)- allow motor neurones to exit the spinal cord
Dorsal roots (posterior/back of the body)- allow motor neurones to enter the spinal cord
7- in the spinal cord, where are the spinal meninges?
Three membranes that surround the spinal cord
Pia mater- inner
Arachnoid layer- middle
Dura mater- outer
8- describe a spinal reflex using the knee-jerk as an example
Tap on the patellar tendon in knee cap
Sensed by stretch receptors in the muscle
Nerve impulses conveyed along sensory pathway into dorsal root ganglion, to terminate in motor neurone
Neurotransmitters released into motor neurone
Generates excitatory potentials
Then generates action potentials
Muscle responds by depolarising and contracting
8- what is a spinal reflex?
An involuntary, stereotypical response of the effector tissue connected to sensory receptors
Allow rapid response to dangerous stimuli
A stimulus to a sensor least to a response in an effector
8- name and explain the two types of spinal reflexes
Somatic- involve skeletal muscle e.g. touching a hot stove and pulling away quickly
Autonomic- involve smooth muscle and glands e.g. bladder sphincter getting too full
8- are spinal reflexes monosynaptic or polysynaptic? What does this mean?
Mostly polysynaptic- they involve interneurons (join sensory neurones with motor neurones in complex way, only found in CNS)
Some may be monosynaptic (join sensory with motor but only contain one space for action potential)
8- what is an interneurone?
Central nodes of neural circuits
Enable communication between sensory and motor neurones in the CNS
9- the autonomic NS is divided into sympathetic and parasympathetic. Compare their functions
SYMPATHETIC- Arousing
One of the two main divisions of the ANS
Main function is to control fight-or-flight response
Control body under threat
Originates in thoracic and lumbar regions of spinal cord
Shorter neurones
Faster system
Heart rate- increases
Lungs- bronchial tubes dilate (more air)
Pupils- dilate
GI System- decreased stomach action
Urinary- decreased urinary output
Adrenaline- released
Saliva- decreases
PARASYMPATHETIC- Calming
One of the two main divisions of the ANS
Main function is to control rest-and-digest and homeostasis
Control body at rest
Originates in sacral regions of spinal cord
Longer neurones
Slower system
Heart rate- decreases
Lungs- bronchial tubes constrict
Pupils- constrict
GI System- increased stomach action
Urinary- increased urinary output
Adrenaline- none released
Saliva- increases
10- where is the medulla in the brain? What is its function?
Location-
Bottom most part of the brain, connects to the spinal cord
Function-
Key conduit for signals to and from brain to body
Controls vital processes like heart beat, blood pressure and breathing
10- where is the pons in the brain? What is its function?
Location-
A part of the brain stem
Function-
Communication- Holds messages and sends them to the correct part of the brain
Handles unconscious processed and jobs. E.g. sleep-wake cycle, breathing, swallowing
10- where is the midbrain in the brain? What is its function?
Location-
Topmost part of the brainstem
Function-
Relay station for auditory and visual stimuli? E.g. eye movement and hearing
10- where is the cerebellum in the brain? What is its function?
Location-
The “little brain”
The part of the brain located at the back of the head, just above and behind the brainstem
Function-
Makes postural adjustments required to maintain balance
Coordination, movement and motor control
10- where is the hypothalamus in the brain? What is its function?
Location-
About the size of an almond
Above the midbrain below the thalamus deep in the centre of the brain
Function-
To keep the body in a stable state of homeostasis- done through ANS communication or hormone release
10- where is the thalamus in the brain? What is its function?
Location-
Egg shaped structure
Near the centre of the brain, above the midbrain
Function-
The body’s relay station
All of the body’s sensory information (except smell) is passed through the thalamus before it is sent to the cerebral cortex for interpretation
10- where is the cerebrum in the brain? What is its function?
Location-
In the forebrain (top and front of the head)
Largest part of the brain
Divided into two cerebral hemispheres, each one controls the opposite side of the body
Contains the major lobes of the brain
Function-
Controls all voluntary movements within the body (with the assistance of the cerebellum)
11- outline how and what CSF circulates
Clear liquid that circulates between the ventricular system and the subarachnoid space
It circulates metabolic products, hormones and neurotransmitters
11- how does CSF relate to the meninges?
CSF passes between two layers of the meninges- between the arachnoid mater and Pia mater is the SUBARACHNOID SPACE
Within this space it slowly circulates throughout the entire perimeter of the CNS
