VETM 3080: Neurophysiology Lecture 9-19

myocyte

muscle cell- single nucleus

myofibre

muscle cell- multinucleated

Sarcolemma

plasma membrane of a muscle fiber

sarcoplasm

cytoplasm of a muscle cell

characteristics of skeletal muscle

cylindrical with myofibres attached to skeleton that may production contraction

Each myofibre has one....

Muscular junction (site of synapase)

myofibrils

bundles of myofilaments made of actin and myosin

arrangement of myofibrils

z-line disk pattern

area between z-line disks

sarcromere

what wraps around each myofibril

T-tubule

what does the SR contain

Calcium between T-Tubules along myofibrils

what is the contractile unit of muscles

sarcomere

what is a sarcomere made of

- actin (thin) anchored at z-line

- myosin (thick) between actin

structure of myosin

2 molecules coil to form tail with 2 heads

structure of actin

- actin

- troponin (attracts Ca)

- tropomyosin (blocks myosin head)

Excitation-contraction coupling mechanism

1. AP in motor neuron causes channels to open and NT released into cleft

2. Ach binds to Nicontinic ACHR on MEP

3. Na enters cell causing depolarization and triggers AP in sarcrolemma

Ryanoide Receptors

site where voltage-gated Ca channels tag onto on SR membrane and allows Ca to enter sarcoplasm from SR

what occurs to actin after Ca released from SR

binds to troponin causing tropomyosin to unblock and allow binding to myosin resulting in contraction

Ratchet theory- Contraction

ATPase in myosin head cleaves ATP

- tilt headgroup allowing new myosin head to release actin

what needs to be supplied for the ratchet theory of contraction to continue

Ca levels

short term energy supply for muscles

Creatine phosphate

order of energy generation for muscle contraction

1. CP

2. glycolytic

3. aerobic

white twitch fibres

- fast twitch

- short contraction time

- large in size

-anaerobic

red twitch fibres

- slow twitch

- long contraction time

- smaller size

- aerobic

mechanism of removal of Ca

Ca ATPase reset my coving Ca out of cell or into SR

PMCA

cell surface Ca ATPase

SERCA

Sarcoplasmic pump

2 mechanisms of smooth muscle

1. Visceral- local stimuli

2. Multi-unit-nervous stimulation

How are bones from the skull formed

Fibrous membrane via intraossification

Bone suture

fusion of adjacent bone

Doliocephalic

long and narrow

Brachiocephalic

short

where do cranial nerves leave skull

foramen

where does the spinal cord exit

foramen magnum

occipital condyles

articulate with atlas

Dental formula- maxillary

3 incisors

1 canine

4 premolars

2 molars

Dental formula- mandibular

3 incisors

1 canine

4 pre molars

3 molars

3 meninges

dura mater, arachnoid mater, pia mater

In what meningeal does CSF circulate?

arachnoid

In what meninge has blood vessels and capillaries

pia mater

2 folds of meninges

1. Falx Cerebri- longitudinal fissure between cerebral hemisphere

2. Tentorum Cerebri- transverse fissure between cerebrum and cerebellum

Site of CSF absorption

arachnoid granulations

Thalamocortex structures

thalamus and cortex

functions of thalamocortex

conscious behaviour, vision, smell

structures of brainstem

pons, medulla oblongata, midbrain

functions of brainstem

basoconscious

what are the 3 divisions of telencephalon

Cerebral cortex, rhinencephalon, basal nuclei

2 folds of cerebral cortex

gyri and sulci

functions of frontal cortex

sensory, behaviour, voluntary, learning

Functions of parietal cortex

sensory and association

functions of temporal lobe

audition, equilibrium

functions of occipital lobe

vision

white mater of cerebral cortex

axons covered my myelin

the 3 fibres in white mater of cortex

association fibres (neurons within same hemisphere)

projection fibres (cortex to the brainstem)

Commissural fibres (hemispheres)

rhinencephalon

Olfactory and limbic

parts of the limbic system

hippocampus, amygdala, hypothalamus

What does the limbic system do?

emotion and behaviours

basal nuclei

collection of gray matter

basal nuclei names

caudate nucleus, putamen, claustrum, Globus pallides

function of basal nuclei

voluntary movement from cortex

3 types of ataxia

proprioceptive, vestibular, cerebellar

definition of ataxia

inability to coordinate activity of limbs, trunk and head

is ataxia a sensory or motor sign

sensory

what part of the brain contains the LGN and MGL

thalamus

lateral geniculate nucleus

vision

medial geniculate nucleus

audition

Hypothalamus

integration of nervous and endocrine system

- control neurohypophysis and adenohypophysis

- secretes releasing hormones

examples of functions of hypothalamus

increase HR, BP, Temp, water balance, food intake

is neurohypophysis a direct section

Yes

Effect of TRH

Increase TSH which increases T3 and T4

Effect of CRH

secretion of ACTH which increases secretion of glucocorticoids, mineralocorticoids and androgens

Effect of GnRH

Stimulates secretion of FSH and LH leading to production of gametes

Effect of prolactin-releasing hormone

stimulates prolactin and increases milk production from mammary gland

effect of GHRH

stimulates GH and increases anabolism and organ growth

Pons

- Give rise to the trigeminal nerve (facial and masticatory)

- communicates with cerebellum

- respiration and micturition

medulla oblongata

- contains nuclei of CN 6- 12

- Relay sensory info from spinal cord (proprioception, temperature, pain)

- motor info from cortex and brainstem

- CV and respiration

which structure of the brain contains ascending RAS

Medulla oblongata

pineal gland

day/night cycle via melatonin

Precursor of melatonin

serotonin

midbrain

sensory (visual and auditory)

- head movement

- motor (pupil contraction)

Cerebellum

compares intended movement with actual movement

- smoothes and corrects via nodular lobe

where does the cerebellum receive info from

cortex (intended) spinal cord (actual)

brainstem reticular formation

receives sensory signals from entire NS and projects into cortex via thamalus

what is ascending RAS responsible for

level of arousal

functions of RAS

locomotion, muscle tone, true pain, micturition

brainstem: respiration

nuclei in medullar and pons control expiration and respiration

brainstem CV regulation

cardiac accelerator centre, contraction strength and inhibitor

where are the cell bodies for somatic motor neurons

nuclei in brain outside CNS

where are the cell bodies for somatic sensory neurons

in ganglia outside CNS

Function of CN1

smell

how to examine CN1

absense or decrease of smell

clinical disease of CN1

anosmia or hyposmia

CNII function

vision

CNII pathway

activate photoreceptors -> AP -> Optic nerve -> optic chiasm -> optic tract

conscious vs unconscious visual perception structure

conscious = LGN

unconscious= Pretectal

CNII examination

PLR and menace

CNII clinical disease

blindness

visual system: medial vs lateral fibres

medial- decussate

lateral- same side

CNIII function

iris constrictor muscle and pupillary constriction

CNIII exam

ventrolateral strabismus and PLR