week 3 (L1 muscle + neurons)

what are the 3 types of muscle

skeletal, cardiac, smooth

what are the 2 major classes of muscle (based on appearance)

• striated

• smooth

main role of muscles

• specialised connective tissue

• responsible for body movement

• controls shape + size of organs

what is striated muscle

• appearance of stripes or striations

• there is two types (skeletal + cardiac)

which two types of muscles are striated in appearance

• skeletal

• cardiac

what is cardiac muscle

heart muscle

what is skeletal muscle

attached to bone

what is smooth muscle + appearance

• no cross striation

• arranged in sheets

• primarily in the walls of hollow organs (maintain shape) eg. iris, ciliary body

• for subtle, sustained, or rhythmic actions

what cells produces the extracellular matrix in collagen

fibroblasts

what is a fascicle

a bundle of muscle fibres

what is the epimysium

connective tissue that wraps around a bundle of fascicles

how much of our body weight to muscles contribute to

40%

what is connective tissue

tissue that

• connects

• supports

• binds or separates other tissues or organs

• eg. sclera, limbus, cornea

what is the 3 main layers of connective tissue of skeletal muscle

“EEPI = EPE = (from inside) Endomysium, perimysium, epimysium

• endomysium = tissue that surround individual muscle fibres

• perimysium = thicker irregular tissue that surround a bundle of muscle fibers (fascicle)

• epimysium = denser irregular tissue that surrounds a bundle of fascicles (forming outer layer of muscle)

  

categories of skeletal muscle fibres (by diameter + natural colour)

• red fibers (slow twitch)

• white fibres (fast twitch)

• intermediate fibers (medium twitch)

what are red fibres

• a type of skeletal muscle fiber

• red fibers are:

  • rich in myoglobin, cytochromes and mitochondria

  • small

  • slow twitch (sustained activity eg. marathon running)

what are white fibres

• a type of skeletal muscle fiber

• white fibres are:

  • poor in mitochondria, cytochromes and myoglobin

  • large

  • fast twitch (rapid, powerful bursts of activity eg. sprinting)

what are intermediate fibres

• a type of skeletal muscle fiber

• intermediate fibers are:

  • medium thickness

  • a third type of muscle fibre that sits between red and white

  • Not as slow as red, not as explosive as white

what are extraocular muscles

• seven specialised skeletal muscles

• controlling eye movement, alignment + eyelid elevation

3 muscle types + their control

skeletal

• voluntary

• eg. moving arm, blinking (to an extent)

smooth

• involuntary

• found in organs eg. ciliary muscle, iris

cardiac

• involuntary

• eg. heart pumping

what are the 2 categories of smooth muscle

visceral (single unit)

• all cells contract together as one joined by gap junctions

• sim} a crowd doing a wave together

• for bulk movement

• 📍 Example:

  • Food moving through intestines
    👉 you don’t need accuracy, just movement

multi unit

• Each cell works independently, no gap junction

• sim} people working individually

• for precise control

• 📍 Example:

  • Changing pupil size slightly

  • Focusing on near vs far objects

what is thyroid eye/ graves disease

• autoimmune disease where immune cells attack the thyroid gland resulting in an excess secretion of thyroid hormone

• immune cells also attack the skeletal muscle and connective tissue = swelling + inhibits movement

what is an autoimmune disease

where the body's immune system mistakenly attacks healthy cells, tissues, and organs instead of protecting them, causing chronic inflammation and damage

what is the bulging of the eye (graves disease) called

proptosis

what are neutrons

specialised cells that pass on information from dendrite to axon terminal (one end to another)

what is myelin sheath

• fatty insulation around a neuron fiber

• signals travel faster with it

• some neurons don’t have it = slower signals

Speed needs:

• Myelinated neurons = signals need to be fast

  • Example: moving your hand away from something hot

• Unmyelinated neurons = speed isn’t critical

  • Example: temperature signals (taking off jacket when hot)

three main categories of neurons (according to function)

• S = Sensory → brings info in to CNS (afferent) (add)

• M = Motor → sends info out of CNS (efferent) (eff off)

• I = Interneuron → inside CNS, connects the two

(sexy men icky!!)

what are synapses

• tiny gap between two neurons

• “message handover area”

what are neurotransmitters

• the chemical messengers that convey messages across the gap (synapse)

neuron-synapse analogy?

🧩 Analogy:

• Neuron 1 = person with a message

• Synapse = empty space / gap between desks

• Neurotransmitter = note that carries the message to the next person (Neuron 2)

• Neuron 2 = person recieving the message

what are glial cells

helpers or caretakers of neurons — neurons do the signaling, glial cells do the maintenance

types of glial cells

“(PNS) Sexy Sisters // (CNS) Excite Any Old Men”

function of different types of glial cells

CNS

• Astrocytes: maintain blood brain barrier and extracellular homeostasis
• Oligodendrocytes: myelinate axons
• Ependymal cells: production of cerebrospinal fluid
• Microglia: macrophages-like, clear cell debris and dead neurons

PNS
• Swann cells: myelinate PNS axons
• Satellite cells: maintain extracellular homeostasis

what is the visual pathway

“R O C O L O”

• R = Retina

• O = Optic nerve

• C = Chiasm

• O = Optic tract

• L = LGN

• O = Occipital cortex

what is optic neuritis

• autoimmune disease

• inflammation of optic nerve

• causes: MS, infection, other immune diseases

• symptoms: pain in eye movement, acute vision loss, colour vision abnormality