Bad lectures Flashcards
What are sensory receptors?
Sensory ending of an afferent neuron or specialized receptor cell
What is adaption in a sensory receptor?
Gradually reduce their response to a constant stimulus
What is modility?
The sensory endings of one sensory unit is the same, and are sensitve to one type of sensation, which is the modality.
–> Some are touch sensitive while some are temperature sensitive
What codes for intensity of the ap?
Frequency of AP and number of axons or motor units acitve
What codes for modality and location?
By the selection of particular axons or motor units to be active along a specific pathway.
What is the receptive feild of the axon?
The area of the body that if stimulated will result in the firing of that axon. Can be characterised by size and density.
What is the difference between small and large receptive fields?
Small ones allow for good localisation of stimulus and large ones allow for bad localisation of stimulus
How many vertabrae are there?
Cervical - 7 Thoracic - 12 Lumbar - 5 Sacrum - 5 fused coccxyx - 2 to 5 fused
How many ribs are there?
24
What bones does the scapula articulate with?
clavicale + humerous
What does the pelvic girdle consist of?
Consists of two hip bones artculating with the sacrum
What does the cerebellum do in movement?
The cerebellum coordinates movements. It does this by using information about current body position to compute movements needed to achieve a new body poistion and check planned movements against actual movements to compute corrections
Brain volventary movement?
Activation of the primary motor cortex is assited by input from the cerebellum and the basal ganglia.
The axons of primary motor cortex neurons project to the spinal cord.
The sensory pathway (dorsal/posterior) pathway?
Three neurons.
1: Cell body in dorsal root ganglion (unipolar), so the peripheral fibre from sensory recptor in skin and central fibre ascends towards brain in spinal cord white matter.
2: Cell body in medulla oblongata, axon crosses to opposite side and ascends
3: Cell body in the thalamus, axon ascends to somatosensory cortex.
The corticospinal pathway –> for volentary movement
Two neurons, upper motor and lower motor
Upper: cell body in primary motor cortex (precentral gyrus), axon extends from motor cortex to spinal cord on opposite side
Lower: Cell body in ventral horn (grey matter) of spinal cord, extends out of the ventral root and into the body –> synapses on skeletal muscle
What is the commisural tract?
Axons cross from side to side
What is the projection tract?
Axons extend between cortex and other CNS areas outside cerebrum
What is the association tract?
Axons on same side within cerebral cortex
Communication between brain areas (short or long distance)
Particular regions for the motor cortex?
Foot –> hand –> face –> tounge
What are the pre and post central gyrus?
Pre –> primary motor cortex
Post –> somatosensory cortex
What are gamma motor neurons?
sensory receptor that changes length in order to maintain steady output and detect changes in length
Always tense as they need to detect changes in length.
What are the structural components of an axon?
Dendrites (recive input, send info to cell body)
Cell body (contains nucleus and organelles, sums input)
Axon (carriers electicaly impulses, may or may not be myelinated)
Axon terminal (end of the axon, neurotransmitter released)
In the CNS a group of cell bodies are?
Nucleus
Group of cell bodies in cerebral cortex or spinal cord
Grey matter
Bundle of axons in cerebral cortex or spinal cord
White matter
Bundle of axons in the CNS
tract
What do astrocytes do?
- -> Supply nutrients to neurons
- -> Ensheath blood capillaries
What do microgila do?
- -> Immune cells
- -> Engluf microorganism
What to ependymal cells do?
- Line flid filled spaces of brain and spinal cord
- Have cilia
What do oligodendrocytes do?
- -> Support nerve fibres
- -> Ensheath them with myeline
Afferent vs effecerent
ascending vs decending
Autonomic efferent pathways (in general)
In general:
Three neurons
1: Cell body in brain, axon in brain or spinal cord
2: Cell body in brain or spinal cord, axon in PNS
3: Cell body in PNS, axon in PNS
Parasynpatheic autonomic efferent
- has long preganglionic (leaves CNS at brainstem and spinal cord levels)
- short post ganglionic
- Secrets ACH
- -> post gang is not myelinated
Causes: Decreased heart rate Increase in gastric motility Decrease in pupil size Increase in salivation
synpatheic autonomic efferent
Has a short axon preganglionic (Leaves CNS at thoracolumbar levels) Secrets norepinephrine (postganglionic with effector in sympathetic)
Causes: Increased heart rate Constricting blood vessels to skin and viscera blood flow to muscles Decreases gastric motility Decrease salivation Increase in pupil size Increase in sweating
Spinal cord start and end
Starts at: Foramen magnum = “big hole”, the opening at the base of the skull
Ends at: inferior border of 1st lumbar vertebra (L1) (doesn’t go down all the way of the vertebral column)
conus medullaris
End is a tapered cone called the conus medullaris (non-neural tissue)
Filum terminale
Filum terminale extends from conus medullaris to end of spinal cavity (anchors the spinal cord; fibrous, non-neural tissue) (Makes sure it doesn’t hit the sack)
How many segments does the spinal cord have?
The spinal cord has 31 segments
One pair (left and right) of spinal nerves comes off each segment
There are 8 cervical spinal nerves (even though only 7 cervical vertebrae)
Spinal nerves exit the vertebral column at the level appropriate to their origin
What does the dorsal side concern itself with?
Dorsal side mostly concerns itself with afferent info (ascending/ sensory). Information from body comes in to the dorsal roots (from PNS into CNS)
What does the ventral side concern itself with?
Ventral side is concerned with motor/ efferent activities. Ventral roots contain the axons of neurons that flow Information from CNS into the PNS (makes contact with effector)
Motor bodies of neurons in the spinal cord?
Somatic motor neurons (cell bodies) in ventral horn
Autonomic motor neurons (cell bodies) in lateral horn
What happens to the spinal nerves once they leave the spinal column?
The spinal nerve splits into a dorsal and ventral ramus (branch).
Motor information of sympathetic nervous system (rami communicantes and sympathetic ganglion)
–> The parasympathetic nervous system goes out to the ventral ramus.
Dural folds?
Falx cerebri (separates cerebral hemispheres; medial plane) (sickle shaped piece of tissue that goes between the two halves of the cerebrum)
Falx cerebelli (separates cerebellar hemisphere; medial plane) (separates the two halves of the cerebellum)
Tentorium cerebelli (separates the cerebrum from the cerebellum; horizontal plane) (separates the cerebrum from the cerebellum - goes in the gap between the two in the posterior of the brain)
Venous sinus function
Dives down between the hemispheres to form dural folds
Located where the two layers of dura mater separate
Collecting veins
They collect 2 things
- Venous blood from the brain
- ‘Old’ CSF after it has cycled through the ventricular system (leaves the brain through venous sinus, which takes it out into the general circulation)
Pia matar?
- Transparent and delicate
- Blood vessels in arachnoid sit on top of pia mater (and go through to supply blood to the brain)
- Adheres to brain and follows gyri and extends into sulci
What are the features of the ventricular system?
- Network of interconnected “spaces” (=ventricles) within the brain
- Filled with cerebrospinal fluid (CSF), which nourishes and protects the brain
- Spaces line with ependymal cells, which circulate the CSF (done by waving cilia) (don’t produce CSF)
- CSF is produced by the choroid plexus
What does cerebral spinal fluid do?
Surrounds the CNS, within the subarachnoid space
Provides support and cushion
Transports nutrients and waste
Produced by choroid plexus within the ventricles.
What is the circulation path?
lateral ventricles
→ 3rd ventricles → cerebral aqueduct → 4th ventricle → subarachnoid space
Within subarachnoid space it flows around the brain and spinal cord
Exit: through arachnoid → granulations into venous sinus
