Human Movement and Sensation Flashcards
What does the Central Nervous System consist of?
Brain and spinal cord
What does the peripheral nervous system consist of?
Peripheral nerves
What is composed of neurons and glia?`
All parts of the CNS and PNS
What are neurons?
Nerve cells
What is the purpose of Neurons?
Cells specialised for transmission of information
What are the functions of the glia?
Support for neurons
What are the structures of the neuron? (4)
Dendrites
Cell body
Axon
Axon terminal
What is the function of a dendrite?
Recieve input
Send information to the cell body
What is the function of the cell body?
Contains nucleus and organelles
Sums input
What is the function of the Axon?
Carries electrical impulses
May or may not be myelinated
What is the function of the axon terminal?
Terminal end of the axon for neurotransmitter release
What is a group of cell bodies called? (CNS)
Nucleus
What is a bundle of axons called? (CNS)
Tract
What is a group of cell bodies in the cerebral cortex or the spinal cord called?
Grey matter
What is a bundle of axons in the cerebral cortex or spinal cord called?
White matter
What is a group of cell bodies called in the PNS?
Ganglion
What is a bundle of axons called in the PNS?
Nerve
What is the input zone of a neuron?
Dendrites and cell body (receives chemical signals from other neurons)
What is the summation zone of a neuron?
Axon hillock
What is the conduction zone of the neuron?
Axon - quite long.
Carries signals from brain areas, spinal cord, or from peripheral sensory receptors.
What is the output zone?
Axon terminals
Contact with input zone of other neurons or effectors.
Release of neurotransmitters
What are the 4 morphological types of neurons?
(DRAW SLIDE 1)
Multipolar
Bipolar
Unipolar
Anaxonic
What is the structure of a multipolar neuron
Multiple processes emanate from the cell body
Lots of places where dendrites stick out of cell body
What is the structure of a bipolar neuron?
2 processes emanate from the cell body
What is the structure of a unipolar neuron?
Once process emanates from the cell body.
Branches into dendrite and axon
What is the structure of an anaxoic neuron?
No distinct axon
All processes look alike
What are the 3 features of astrocytes?
Supply nutrients to neurons
Ensheath blood capillaries
Injury response
What is the function of a microglia (2)?
Immune cells of the CNS
Engulf microorganisms and debris
What are the 2 function of ependymal cells?
Line fluid-filled spaces of brain and spinal cord
Have cilia to circulate CSF
What are the 2 functions of Oligodendrocytes?
Support nerve fibres
Ensheath them with myelin
What is the function of glia in the PNS?
Support peripheral nerve fibres
Ensheath them with myelin
What are the 4 types of glia in the CNS?
Astrocytes
Microglia
Ependymal Cells
Oligodendrocytes
What is the Schwann Cell?
Plasma membrane wrapped around an axon
What is a myelin sheath?
Lipid fat around an axon
What is the function of a myelin sheath?
Increases conduction velocity
What is a node of Ranvier?
Gaps between myelin
Increase conduction velocity
What is a synapse?
Neurotransmitter release between neurons
What is a synaptic cleft?
When the signal is changed from electrical, to chemical, to electrical, between neurons.
What is a synaptic vesicle?
Little packets of neurotransmitter in presynaptic neuron
What is it called when information goes into the brain
Afferent (ascending)
What is a response that comes out of the brain called?
Efferent (descending)
What is the myelin sheath in the CNS made up of?
Oligodendrocytes
What is somatic in terms of information transmitted?
They are the stuff that we are aware of?
What is an example of somatic efferent?
Running
What is an example of somatic afferent?
Seeing
What is autonomic?
Involuntary
What is an autonomic efferent example?
Heartbeat
What is an autonomic afferent example?
Blood pressure
What is the upper motor neuron located?
Cell body in brain
Axon in spinal cord
Where is the lower motor neuron located?
Cell body in the spinal cord
Axon in the spinal nerve
Is the upper or lower motor neuron myelinated?
Both are myelinated
What is the neurotrasmitter responsible for communication between effector cells?
Ach (Acetylcholine)
What is the effector for the somatic efferent division?
Skeletal muscle
What are the 2 divisions of the autonomic efferent nervous system?
Sympathetic
Parasympathetic
What are the effectors of the Autonomic Efferent nervous system? (4)
Smooth muscle and cardiac muscle
Glands, adipose (fat)
Where is neuron 2 of the autonomic efferent nervous system
Cell body in brain or spinal cord
Axon in PNS
Where is neuron 3 in the autonomic efferent nervous system?
Cell body in the PNS
Axon in the PNS
Is neuron 2 myelinated or unmyelinated?
Myelinated
What neuron 3 myelinated or unmyelinated
UNmyelinated
Where does neuron 2 synapse?
Autonomic ganglion
Is neuron 2 pre- or post-ganglionic?
Pre-ganglionic neuron
Where does neuron 3 synapse?
Effector organ
Is neuron 3 pre- or post-ganglionic?
Post-ganglionic neuron
What is the neurotransmitter for neuron 2?
ACh
What is the neurotransmitter for neuron 3?
ACh or norepinephrine (NE)
What is the function of the sympathetic nervous system?
Prepares body for stress responses e.g. fight or flight
What is the function of the parasympathetic nervous system?
Prepares body for restful situations
What is the neurotransmitter for the sympathetic nervous system?
NE
What is the neurotransmitter for the parasympathetic nervous system?
ACh
What ganglion (para/sympathetic) has a short preganglionic axon and a long postganglionic axon?
Sympathetic
What ganglion (para/sympathetic) has a long preganglionic axon and a short postganglionic axon?
Parasympathetic
What ganglion (para/sympathetic) is close to the CNS?
Sympathetic
What ganglion (para/sympathetic) is far from the CNS?
Parasympathetic
Where are the sympathetic chain ganglia located?
On either side of the vertebral column
How many pairs are there in the sympathetic chain ganglia?
21-23
How long are the fibres of the sympathetic pathway?
Preganglionic (short)
Post (long)
How long are the fibres of the parasympathetic pathways?
Preganglionic (long)
Post (short)
Where is the preganglionic sympathetic pathway located?
Spinal cord (thoracolumbar)
Where is the postganglionic sympathetic pathway located?
Sympathetic chain
Where is the preganglionic parasympathetic pathway located?
Craniosacral (brainstem)
Where is the parasympathetic postganglionic pathway located?
In or near effector
How does a chemical signal get converted into an electrical signal?
A chemical signal (transmitter) opens chemically gated ion channels by binding to them, allowing Na and K to flow.
If -60mV is reached, action potential will begin
How are chemically gated ion channels closed?
Neurotransmitter unbinds
How are voltage-gated ion channels opened and closed?
Membrane is depolarised causing it to open.
Once membrane threshold is changed, the channel will inactivate or close
How are mechanically gated ion channels opened and closed?
Stretch or squish causes the membrane to deform, causing the channel to change shape.
When the membrane returns to the original shape, the channel closes.
What are the chemically gated ion channels in a neuron?
Dendrites and cell body
What are the voltage gated ion channels in a neuron?
Axon hillock, axon, and axon terminals
What is the charge of the inside of a cell regularly?
-70mV
Which direction will sodium move if Na+ channels are opened?
Into the cell
What is a local potential?
Change in membrane potential voltage in a localised area.
How does a local potential occur?
Neurotransmitter binds and opens chemically-gated ion channels on dendrites/ cell body, either allowing Na in or K out.
What are the two forms of local potential?
Excitatory or Inhibitory
How does an EPSP form?
Excitatory local potentials form when a presynaptic neuron releases an excitatory neurotransmitter which opens Na gates, causing Na to enter and the cell to depolarise.
What causes IPSPs to form?
When a presynaptic neuron releases an inhibitory neurotransmitter, which opens K gates, causing K to leave the cell and hyperpolarise.
What are the two ways that local potentials can be summed?
Spatial and Temporal Summation
Describe spatial summation
This is the sum of the input from multiple presynaptic neurons
Describe temporal summation
This is the sum of the input from the repeated firing of one pre-synaptic neuron
Where are presynaptic inputs summed?
Axon-hillock
What are the steps of action potential?
- Depolarisation of threshold
- Rapid depolarisation due to entry of Na
- Repolarisation due to exit of K
- Hyperpolarisation due to exit of K
- Return to resting membrane potential, all channels close
How does an electrical signal trigger a chemical signal
Na diffuses from the axon hillock to initiate a AP in the initial segment of the axon
AP propagates to each neighbouring axon segment (for unmyelinated axons) or node (myelinated) in one direction
AP arrives at the axon terminals causing the Ca channels to open
Ca enters the terminals, causing the release of neurotransmitter in the synaptic cleft
What stimulates the action potential in the initial segment?
Rapid depolarisation of a flood of Na entering the axon hillock.
Describe AP propagation in unmyelinated axons
Membrane potential depolarises to 30mV in initial segment
Na spread away from channels to bring segment 2 to threshold.
This causes an action potential to develop in segment 2. The initial segment begins repolarisation.
Na spreads to segment 3 and that begins to reach threshold.
The action potential only can only move forward, not backward as the membrane enters absolute and refracts.
How fast do AP propagate along unmyelinated axons?
1-5m/s
Are myelinated or unmyelinated axons faster for AP conduction?
Myelinated
Do Nodes of Ranvier have high or low concentrations of VG channels?
High
Describe AP propagation in myelinated axons
AP develops in the initial segment
Local current causes depolarisation which brings axolemma at node 1 to threshold
AP develops at node 1
Process repeats
In what refractory period can a 2nd AP be generated?
Relative refractory period.
When does the absolute refractory period happen?
When the VG Na channels are already open or become inactive. (when depolarisation is occurring)
When does the relative refractory period occur?
When some Na channels begin to shift from an inactive to closed state.
What are the 3 key features of a chemical synapse?
Presynaptic axon terminal
Synaptic cleft
Postsynaptic cell
What happens in the presynaptic terminal during a chemical synapse?
VG ca channels on the terminal membrane
Synaptic vesicles filled with neurotransmitter
What happens in the synaptic cleft during a chemical synapse?
A space neurotransmitter diffuses across
Enzymes that inactivate neurotransmitters are present in the cleft
What happens in the postsynaptic cell during a chemical synapse?
There are chemically gated ion channels
What happens when the axon terminal is depolarised during synaptic transmission?
Ca channels open and Ca moves down the gradient into the terminal
What happens at the release of the neurotransmitter during synaptic transmission?
Ca interacts with vesicles which cause them to release a neurotransmitter into the synaptic cleft
What forms the local potentials during synaptic transmission?
Neurotransmitter binds to chemically-gated ion channels on the post-synaptic cell, causing EPSPsor IPSPs.
What happens at the end of the synaptic transmission?
The neurotransmitter unbinds from the chemically gated channels.
Enzymes degrade the neurotransmitter and are recycled back to the axon terminal.
What is a key feature of the neuromuscular junction?
Specialised type of chemical synapse between axon terminal of a motor neuron and a skeletal muscle fibre
Is a neuromuscular junction excitatory or inhibitory?
Excitatory
What kind of synapse does the NMJ have?
Cholinergic
How many synaptic transmissions is needed to bring the muscle membrane to threshold?
1
How big are neuron to neuron transmission?
Tiny
How big are neurons to skeletal muscle synapses?
Huge
What kind of neurotransmitters are used in neuron to neuron transmission verus muscle transmission?
In muscle, only ACh is used, whereas in neuron to neuron, there is a variety.
What is the purpose of an electrical synapse?
They allow for faster depolarisation. They are rare and found in cardiac muscle.
What is the definition of a chemical synapse?
Presynaptic neuron releases neurontransmitter to bind to receptors on postsynaptic neuron.
What is definition of a neuromuscluar junction?
Specialised chemical synapse between a motor neuron and skeletal muscle.
What is the definition of an electrical synapse?
An electrical connection where ions flow directly from the presynaptic to postsynaptic cell through a gap junction.
Where does the spinal cord start?
Foramen magnum
Where does the spinal cord end?
Inferior border of the 1st lumbar vertebra
What is the sac that the spinal cord sits in made up of?
Meninges
Where is the spinal cavity?
Within the vertebrae, in the spinal canal
Where does the spinal cavity extend to?
To the coccygeal vertebrae
What is the meningeal sac filled with?
Cerebrospinal fluid (CSF)
What is the end of the spinal cord called?
Conus Medularis
Where does the filum terminale attach to?
Conus Medularis to the spinal cavity - end of meningeal sac
What is the purpose of the Filum terminal?
Anchors the spinal cord
How many segments does the spinal cord have?
31 pairs
Cervical - 8
Thoracic - 12
Lumbar - 5
Sacral - 5
Coccygeal - 1
Are spinal nerves named for the vertebra they exit above or below?
Below, with the cervical nerves being an exception to this rule
Where does the first cervical spinal nerve exit from?
Between the skull and the first cervical vertebra
Draw the internal anatomy of the spinal cord
Lecture 5
What is white matter made of?
Axons
What is grey matter made of?
Cell bodies
What is the dorsal horn made of?
Cell bodies
What is the ventral horn made of?
Cell bodies
What is the ventral column made of?
Axon
What is a ganglion?
Group of cell bodies
What is a nerve root made of?
Axons
What is a dorsal root ganglion made of?
Cell bodies
On which side (dorsal or motor) is the sensory pathway
Dorsal
Where does the efferent information leave through?
Ventral roots
What is the front of the spinal column called?
Ventral side
Where is the lower motor neuron located?
In the ventral horn
Where are the cell bodies of the sensory neurons located?
In the dorsal root ganglion
Where does the output zone enter the spinal cord?
Through the dorsal roots
Where are the cell bodies of sensory neurons located?
In the dorsal root ganglion
Do dorsal nerve roots carry afferent or efferent information?
Afferent
Which nerve roots carry efferent information?
ventral nerve roots
What is a ramus?
A branch in which information flows once the nerves have left the vertebral column
Draw a diagram of a peripheral nerve
lecture 5
Axons covered in endoneurium
These are bundled together to form a fasicle
The fascicles are covered in perineurium
Fascicles are bundled together to form a nerve
nerves are covered in epineurium
What are the 3 layers of meninges on the brain?
Dura mater
arachnoid
Pia mater
What are the 5 features of dura mater?
Outermost layer
Tough
Inner and outer layer
Space between layers forms venous sinuses
Inner layer forms dural folds
What are the 3 features of dural folds?
Formed from inner layer of dura mater
Separates major divisions (halves) of the brain
Provide stability of the brain within the cranium
What are the 3 types of dural folds? Draw
Lecture 6
Falx Cerebri
Falx Cerebelli
Tentorium Cerebelli
What is the purpose of the falx cerebri?
Seperates the cerebral hemispheres on the median plane
What is the purpose of the falx cerebelli?
Seperates cerebellar hemispheres on the median plane
What is the purpose of the tentorium cerebelli?
Seperates the cerebrium from the cerebellum on the horizontal plane
What are 3 features of the venous sinus?
Located between the two layers of dura mater
Collect veins
Collect venous blood from the brain and old CSF.
What are 3 features of the arachnoid layer?
Does not extend in sulci
Contains subarachnoid space and arachnoid granulations
Contains blood vessels
What are the features of the subarachnoid space?
Filled with CSF
What are the features of the arachnoid granulations
Perforate the inner layer of dura mater
Transport old CSF from subarachnoid space into venous sinus
What are 4 features of the pia mater?
Inner layer of the meninges
Transparent and delicate
Blood vessels in arachnoid sit on top of pia mater
Adheres to brain to adhere to gyri and extend to sulci
What are 4 features of the ventricular system?
Network of interconnected spaces within the brain
Filled with CSF (nourishes the brain)
Space willed with ependymal cells
CSF produced by choroid plexus
Draw the ventricular system
Bottom of NM 6.
What are 4 features of Cerebrospinal Fluid?
Produced by the choroid plexus
Surrounds the CNS within the subarachnoid space
Provides support and cushion
Transports nutrients and waste
What is the circulation path of the CSF?
3rd ventricle
Cerebral Aqueduct
4th Ventricle
Subarachnoid space
Flows around the brain and spinal cord
Exits through the arachnoid granulations into venous sinus
Draw the external anatomy of the brain
Lecture 7
What does the lateral sulcus seperate?
Temporal lobe from the frontal and parietal lobes
What does the transverse fissure seperate?
Cerebrum from the cerebellum
What is associated with the front lobe?
Language, personality (bottom)
Motor control (top)
What is the parietal lobe associated with?
Somatosensory
What is the occipital lobe associated with?
Vision
What is the temporal lobe associated with?
Memory
hearing
Draw the internal major divisions of the brain (medially)
Lecture 7
What is the corpus callosum made from?
White matter
What are the 3 types of white matter?
Commissural Tracts
projection tracts
Association tracts
What is the purpose of commissural tracts?
Axons cross from side to side, good for co-ordination
What is the purpose of projection tracts?
Axons extend between cortex and other CNS areas outside cerebrum
What is the purpose of association tracts?
Axons on same side of cerebral cortex
Communication between brain areas on the same side
Where is the primary motor cortex located?
Pre central gyrus
What primary cortexes are in the post central gyrus?
Somatatosensory and motor
What is the corticospinal pathway?
Upper motor neurons and their cell bodies
Where does the upper motor neuron synapse?
On the lower motor neuron
Where does the lower motor neuron synapse?
On the skeletal muscle
Where is the axon and cell body of the upper motor neuron?
Cell body in the primary motor cortex
Axon extends into spinal cord on the opposite side
Where is the cell body and the axon of the lower motor neuron located?
Cell body in the ventral horn.
Axon extends into the spinal cord
What happens when there is damage to the primary motor cortex?
Muscle weakness and paralysis on the opposite side.
Describe the function of neuron 1 in the dorsal/posterior column pathway
Cell body in the dorsal root ganglion
Input zone in from skin
Central fibre extends towards the brain
Synapses onto neuron 2 in Medulla Oblongata
How many neurons are there between the sensory receptor and the somatosensory neuron in the postcentral gyrus (dorsal/posterior column pathway)
3
Describe neuron 2 in the dorsal/posterior column pathway
Cell body in medulla oblongata
Axon crosses to opposite side and ascends
Make synapse on neuron 3 in the thalamus
Describe neuron 3 in the dorsal/posterior column pathway
Cell body in the thalamus
Axon ascends to the somatosensory cortex
What happens when there is damage to the somatosensory cortex?
No place for information to go, no perception of touch in that area
What is sensory transduction?
Conversion of a sensory stimulus to an action potential
What are the 4 types of information encoded by neural activity?
Modality
Duration
Intensity
Location
What is modality?
Type of stimulus detected by a specific type of receptor
What are the 4 modalities of stimulus
Thermoreceptor
Chemoreceptor
Mechanoreceptor (tactile receptor)
Mechanoreceptor (proprioceptor)
Mechanoreceptor (baroreceptor)
Nocieceptor
What is the purpose of a thermoreceptor?
detecting relative temperatures
What is the purpose of a chemoreceptor?
Detecting chemicals (O2, CO2) in blood
What is the purpose of a Mechanoreceptor - tactile
Detects light touch, pressure, and texture
What is the purpose of a mechanoreceptor - proprioceptor
Detects limb position in relation to the trunk, stretch in muscle, or tendon
What is the purpose of a mechanoreceptor - baroreceptor?
Detects pressure within the body e.g. blood vessels, airways
How do thermoreceptors work?
Nerve endings with temperature gated ion channels
Fast adapting
Channels open to let Na in to depolarise membrane, if threshold is reached, AP will be fired to brain
How do chemoreceptors work?
Chemically gated ion channels.
Channels open, Na enters and depolarises, if threshold is reached, AP will fire to brain
How to mechanoreceptors work?
Mechanically-gated ion channels
Physical forces distort the plasma membrane
Channels open, Na depolarises membrane, if threshold is reached, then the AP will fire to the brain
Are tactile receptors fast or slow acting?
Fast adapting
Are proprioceptors fast or slow acting?
Slow acting because we don’t need to know where our limbs are at all times
How do nociceptors work?
Can be temperature, chemically, or mechanically gated.
Slow adapting and responds to extreme stimuli.
Is tonic or phasic a fast adapting receptor?
Phasic
Describe the activity of a tonic receptor?
Constantly active in the background.
When stimulus arises, the AP frequency will change.
Describe the activity of a phasic receptor
Normally silent.
Will send action potentials if there is a change but will stop quickly if it is not painful.
How does AP frequency change in response to a stimulus?
No AP = no sensation
Some AP = some sensation
More AP = more intense sensation
Which receptors are slow adapting?
Tonic
What are the 2 factors that influence sensitivity?
Size and density of receptive fields.
How many recepetive fields are there per neuron?
1
What do largely spaced receptive field provide?
Less sensitivity
Draw the map of neural interactions
Lecture 9
How is movement planned in the brain?
Prefrontal cortex will make decisions to move and plan outcome
The premotor cortex will organise the movement sequences required
How is movement initiated?
The primary motor cortex have neurons involved in directing voluntary movement
What is the purpose of the basal nuclei?
Influences posture and modifies movements.
Refines automatic movements by altering sensitivity of neurons by projecting into other corticospinal pathways
What is the purpose of the cerebellum in modifying movement?
Facilitates learning and execution of motor programs. Organises timing of muscle contractions.
What are the 4 pathways of movement control?
Prefrontal cortex
Premotor cortex
Primary motor cortex
Basal nuclei and cerebellum
Describe the corticospinal Pathway
Upper motor neurons fire AP extending into spinal cord
Activate lower motor neurons in the spinal cord which fire AP along axons within peripheral nerves
Finishes in skeletal muscle
What is a motor unit?
Single lower motor neuron with skeletal muscle fibres
What is the purpose of a small motor unit?
More precise movement as there are fewer surrounding muscle fibres
What is the purpose of a large motor unit?
Activated any muscle fibres and provides forceful movement (of limbs)
Where do the signals of the left cortex control?
Right side of the body
Do voluntary movements have a complex or simple circuit of neurons?
Complex
What is the variable latency of voluntary responses?
100+ ms
What is the latency of reflex movements?
30-40ms
What are stretch receptors?
They detect muscle stretch
What is the structure of a muscle spindle?
Dendrite ends of nerves wrap around muscle fibres
Dendritic endings have mechanically gated Na channels
How does a stretch reflex response happen?
Tendon tap causes contraction of muscle
Muscle spindles get stretched
Mechanically gated channels open the dendritic endings of the sensory neurons
Depolarisation causes an AP
Synaptic transmission causes depolarisation in motor neuron
AP fires along the motor axon to the NMJ
This stimulates a contraction, causing foot to kick.
How does a withdrawal reflex happen?
Nociceptors activated
Sensory neuron depolarises and AP fires
Sensory neuron stimulates interneurons, which stimulate motor neurons that cause flexion and inhibits those that cause extension.
This makes the limb withdraw
What is latency?
Time delay between a stimulus and a response
