Med 1001 (II) Flashcards
1
Q
Describe what the epimysium is
A
It’s connective tissue that surrounds the entire muscle
2
Q
Describe what the perimysium is
A
Connective tissue surrounding fascicles (groups of muscle cells/fibers)
3
Q
Describe what the endomysium is
A
Fine connective tissue surrounding individual muscle cells/fibers
4
Q
Compare and contrast direct and indirect muscle attachment
A
Directly: Epimysium of muscle is fused to periosteum (around bone) of bone or perichondrium of cartilage
Indirectly: Connective tissue wrappings extend beyond muscle as a rope-like tendon or sheetlike aponeurosis
5
Q
What is a muscle origin?
A
Attachment of muscle which stays relatively fixed during muscular contraction
6
Q
What is a muscle insertion?
A
Moveable part or attachment of muscle
7
Q
What is the relationship between muscle insertion and origin?
A
Muscles never push, they always pull. Contractions of muscle fibers will pull insertion towards the origin, shortening the muscle
8
Q
What is a prime mover?
A
Muscle that provides the major force for the specific movement
9
Q
What is a muscle antagonist?
A
Muscle that opposes or reverses a particular movement
10
Q
What is a synergist?
A
Helps or aids prime movers by adding extra force to the same movement or by reducing unnecessary movements
11
Q
What is a fixator?
A
Synergists that immobilise a bone to provide stability for the action of a prime mover
12
Q
What muscle groups are responsible for elevating and depressing your shoulders?
A
Trapezius (superior fibres) - elevation
Trapezius (inferior fibres) - depression
13
Q
What muscle groups are responsible for bending your upper body at the hip forwards and backwards?
A
Erector spinae (extension thus extensors) (allows us to bend back)
Rectus abdominis (flexion thus flexor) (allows us to bend forward like a crunch)
14
Q
What muscle groups are responsible for movement of your chin?
A
Temporalis - horizontal fibres (retrusion, pushing the chin in)
Lateral pterygoid (protrusion, pushing chin out)
15
Q
What muscle group is responsible for abduction and adduction of your legs?
A
Gluteus medius (abduction)
Adductors (adduction lol)
16
Q
What muscle groups are responsible for adduction and abduction of arms?
A
Supraspinatus + deltoid (middle fibers) (abduction)
Latissimus dorsi (adduction)
17
Q
What muscle groups are responsible for flexing and extending your arms forwards and backwards?
A
Posterior delt + Latissimus dorsi (extension or backwards)
Anterior delt - (flexion or forward)
18
Q
What muscles are responsible for flexion and extension of your hand towards your shoulder?
A
Brachialis (flexion)
Triceps brachii (extension)
19
Q
What muscles are responsible for pronation and supination? Note this movement is in axial plane
A
Biceps brachii (supination)
Pronator teres (pronation)
20
Q
What muscles are responsible for flexing and extending your hand?
A
Extensor digitorum (extension)
Flexor carpi radialis + flexor carpi ulnaris (flexion)
21
Q
What muscles are responsible for flexing and extending fingers?
A
Flexor digitorum superficialis (flexion)
Extensor digitorum (extension)
22
Q
What muscles are responsible for flexing and extending your thumb? (pulling the thumb into and away)
A
Flexor pollicis longus (flexion)
Extensor pollicis longus (extensor)
23
Q
What muscles are responsible for adduction and abduction of thumb?
A
Abductor pollicis brevis (abduction)
Adductor pollicis (adduction)
24
Q
What muscles are responsible for extension and flexion of whole leg from hip?
A
Gluteus maximus (extension)
Iliopsoas (flexion)
25
What muscles are responsible for flexion and extension of leg from knee?
Hamstrings (flexion)
Quadriceps femoris (extension)
26
What muscles are responsible for plantarflexion and dorsiflexion?
Triceps surae (plantarflexion)
Extensor digitorum longus (dorsiflexion)
27
What muscles are responsible for inversion and eversion?
Fibularis longus (eversion)
Tibialis anterior (inversion)
28
What is the general location of the heart?
In mediastinum between second rib and fifth intercostal space
Two thirds of it is left of mediastinal line
29
What is the outermost membrane that covers the heart?
Pericardium
30
Describe what the phrenic nerves are and theor function
A pair of nerves that are the primary source of sensory fibres from pericardium. Pain sensations are carried by phrenic nerves are referred to C3 - C5 dermatomes
31
What is the anterior surface of the heart mainly composed of?
Mainly right ventricle + right atrium + little bit of left ventricle
32
What is the posterior surface of the heart mainly composed of?
Mainly left ventricle + left atrium
33
What is the purpose of the coronary arteries and where can you find them/where do they originate?
They supply myocardium and epicardium
Can be found at base of ascending aorta
34
What does the phrase, the heart feeds itself first, mean?
The heart has arteries which means that the blood being pumped is first pumped to the blood, thereby feeding it
35
What is unique about the pulmonary veins?
Although veins usually carry deoxygenated blood back to the heart, the pulmonary veins carry oxygenated blood to the left ventricle
36
Where do the vena cavae (superior and inferior) deliver de-oxygenated blood?
Right atrium
37
What is the purpose of the coronary sinus and where is it located?
The coronary sinus is the largest coronary vein, located on the heart
It delivers deoxygenated blood from the myocardium to the right atrium
38
What are all the names for the right atrioventricular valve?
Tricuspid vale + Right atrioventricular valve
39
What are all the names for the left atrioventricular valve?
Bicuspid valve + Mitral valve + left atrioventricular valve
40
Why is the left ventricle wall thicker than the right wall?
It has to pump all the blood to the rest of the body so it needs a lot of contractile tissue to pump it
41
What is the fossa ovalis?
It's a remnant of an opening between the two sides of the heart which existed when you were a kid in the womb
42
Compare and contrast the pulmonary valve with the aortic valve
Pulmonary valve: Located between right ventricle and pulmonary artery
Aortic valve: Located between left ventricle and aorta
43
Give an overview of heart conduction from an anatomical perspective
Sinuatrial node which is in the right atrium, is the pacemaker of the heart. When stimulated, it sends a signal to the AV (atrioventricular) node. The AV node goes down and is connected to the papillary muscles. When papillary muscles contract, they push the valves open, allowing blood to go from the right atrium to the right ventricle (tricuspid in this case)
44
Describe the role of sympathetic innervation in the heart and where the pre-synaptic and post-synaptic fibres are hooked up
- There are pre-synaptic sympathetic fibres from IML (intermediolateral) nucleus of T1- T5
- Sympathetic stimulation leads to increased heart rate, increased force of contractions and indirectly dilating coronary arteries by inhibiting their constriction
- Supplies more oxygen and nutrients to myocardium during increased activity
45
Describe the role of parasympathetic innervation in the heart and where the pre-synaptic and post-synaptic fibres are hooked up
- Pre-synaptic fibres from vagus nerve (CN X)
- Post synaptic fibres from intrinsic ganglia located near SA and AV nodes
- Parasympathetic stimulation decreases heart rate, decreases force of contraction and constricts coronary arteries
46
Compare and contrast the two 'circuits' of the circulatory system
Right side receives deoxygenated blood from tissues, which is pumped to the lungs to get rid of CO2 and to pick up O2 via the PULMONARY CIRCUIT (receives blood coming back from systemic)
Left side receives oxygenated blood from lungs. Pumps to body tissues via SYSTEMIC CIRCUITS (receives blood coming from pulmonary)
47
Detail the blood flow from the heart to body
Superior and inferior vena cavae + coronary sinus -> Right atrium -> right ventricle -> pulmonary trunk -> pulmonary arteries -> lungs -> pulmonary veins -> left atrium -> left ventricle -> aorta -> body
48
List all the branches of the aorta (top to bottom)
Right/Left common carotid arteries
Right/Left Subclavian arteries
Brachiocephalic
Right/Left coronary arteries
Celiac arteries
Superior mesenteric
Renal
Gonadal
Inferior mesenteric
Common iliac
49
What is the function of the nasal conchae?
Increase surface area of mucousa that warms and humidifies air
50
What are the 4 paranasal sinuses and what are they named after? (FESM)
Named for the bones they occupy:
- Frontal
- Ethmoidal
- Sphenoidal
- Maxillary
51
Describe the structure of the paranasal sinuses
Respiratory epithelium (pseudostratified columnar with cilia)
Filled with air, lightens weight of viscerocranium
Communicates with nasal cavity through small ostia
Assist in warming and humidifying inspired air
They add resonance to voice
Drain mucous to nasal cavities via cilia
52
Outline the pathway of air during inspiration
Enter nostrils => nasal cavity => nasopharynx => oropharynx => laryngopharynx => trachea => bronchi => bronchioles => alveoli
53
Why is the left lung smaller than the right lung?
- Heart is situated mainly on the left side of the heart
. Left lung: 2 lobes (superior, inferior)
*Right lung: 3 lobes (superior, middle, inferior)
*Oblique fissure in both.
*Horizontal fissure in right lung only
54
Outline the differences between the left and right bronchi alongside the consequences this has
It's wider and more vertical so stuff is more likely to get stuck in the right bronchus rather than the left
55
What is the cartilage in the trachea called?
Hyaline
56
What are the cartilages in the trachea held together by?
Anular ligaments
57
What is the cricoid cartilage and what is the difference between it and other cartilage?
Near the top of the trachea, it's the only fully circular cartilage ring in the trachea
58
List all conducting parts (air carrying parts) of respiratory system
Trachea
Bronchi
Bronchioles
Terminal bronchioles
59
List all respiratory parts (gas exchange) of the respiratory syste,
Respiratory bronchioles
Alveolar ducts
Alveolar sacs
60
What is the function of cartilaginous plates in the respiratory system?
Maintains patency of airways
61
What are the two kinds of pleura and outline their differences?
Visceral - cover/line the lungs
Parietal - lines internal thoracic cavity
Pleural fluid exists between the two serous (serum producing) membranes
62
Describe the diaphragm during inspiration and expiration
Expiration:
- Right dome reaches as high as 5th rib and left reaches as high as 5th intercostal space
Inspiration:
- Central tendon moves inferiorly and the domes 'flatten' out
63
Describe the bronchial arteries
Branch from descending aorta and run along branching bronchi to supply blood to all lung tissue EXCEPT to alveoli
64
Describe the pulmonary arteries
Pump deoxygenated blood from heart to lungs
Originate from pulmonary trunk (right ventricle)
One artery each side of the lung
65
Describe the bronchial veins
- Drain lung tissue near roots
- Right bronchial vein connected to azygos vein
- Left bronchial vein connected to accessory hemiazygos or left superior intercostal vein
(rest of blood is drained by pulmonary veins)
66
Describe the role of the pulmonary veins
*Pulmonary veins pump OXYGENATED blood from lungs back to heart.
*Enter left atrium of heart.
*TWO pulmonary veins on each side.
67
List the lymphatic tubes from smallest to largest
L Capillaries, L vessels, L trunks, L ducts
68
What are the primary lymphatic structures?
Red bone marrow
Thymus
69
What are the secondary lymphatic structures?
Lymph nodes
Spleen
Tonsils
Nodules (MALT)
70
What are the functions of the lymphatic system?
1. Helps the immune system by housing and
transporting immune cells.
2. Helps the cardiovascular system by returning
extra-cellular fluid.
71
Describe lymphatic capillaries
Similar to blood capillaries, except
=> Very permeable (take up cell debris, pathogens, and
cancer cells)
=> Endothelial cells overlap to form one-way minivalves,
and are anchored by collagen filaments, preventing
collapse of capillaries
* Lacteals: specialized lymph capillaries present in
intestinal mucosa
=> Absorb digested fat and deliver fatty lymph (chyle) to
the blood
72
What is the importance of valves in lymphatic and circulatory system?
They prevent backflow of fluid
73
Describe lymphatic collecting vessels
Similar to veins, except
Have thinner walls, with more internal valves
74
How are lymphatic trunks formed?
union of the largest collecting ducts
75
Describe the two main lymphatic ducts
Lymph is delivered into one of two large ducts
Right lymphatic duct drains the right upper arm and the right side of the head and thorax
Thoracic duct arises from the cisterna chyli and drains the rest of the body
76
Where do the lymphatic ducts release lymph fluid and how is lymph fluid propelled?
Each empties lymph into venous circulation at the
junction of the internal jugular and subclavian veins on
its own side of the body
* Lymph is propelled by:
=> Pulsations of nearby arteries
=> Contractions of smooth muscle in the walls of the
lymphatics
77
What parts of the body does the right lymphatic duct drain?
right upper arm and right side of head and thorax
78
What are the areas of the body does the thoracic duct drain?
arises as cisterna chyli; drains rest of body except for right upper arm, right side of head and thorax
79
What is the main function of primary lymphatic structures?
Involved in formation and maturation of lymphocytes
80
What is the main function of secondary lymphatic structures?
House lymphocytes and other immune cells.
Site of initiation of immune response.
81
Describe red bone marrow
Site of hematopoiesis (production of red blood cells, white blood cells, platelets etc).
* B-lymphocytes (B-cells) are a type of white blood cell made in bone.
82
Describe the thymus
anterior superior mediastinum
* main function of thymus is antigen-independent maturation of T lymphocytes
* max size at puberty (30-40g)
* atrophies and replaced by fat in adulthood
83
Describe where you can find lymph nodes and what they are
Secondary lymphatic structures.
* Embedded in connective tissue, in clusters along
lymphatic vessels.
* Near the body surface in cervical, axillary, and
inguinal regions of the body.
84
What is the function of lymph nodes?
1. Filter lymph —macrophages destroy microorganisms and debris
2. Immune system —lymphocytes are activated and mount an attack against antigens
85
What is the structure of a lymph node?
Bean shaped with an external fibrous capsule
* Two histologically distinct regions
[Cortex]: Cortex contains follicles with germinal centres
[Medulla]:Lymph sinuses contain macrophages
* T cells circulate continuously among the blood, lymph nodes, and lymphatic stream
86
Describe the spleen
* located in the Left hypochondrium
* Filters blood
* White pulp = lymphoid tissue
* site where immune response initiated against substance in blood
87
What are the three kinds of tonsils?
Lingual tonsils
Palatine tonsils
Pharyngeal tonsils
88
What are the kinds of lymphatic nodules?
Ileum and appendix
89
Describe the structure and innervation of the lips alongside the artery which supplies it
- Comprised of orbicularis oris muscle
- Innervated by branches of facial nerve (CN VII)
- Blood supply by branches of facial artery
90
What is teeth made of and where is it located?
* Made of dentin covered in enamel (hardest substance in body).
* Located in maxilla & mandible.
91
Compare and contrast the anterior tongue vs posterior tongue
* Anterior: oral ectoderm, smoother, taste by facial nerve CN VII
* Posterior: foregut endoderm, lumpier, taste by glossopharyngeal nerve CN IX.
* General sensation for all of tongue is by lingual branch of trigeminal nerve CN V.
92
Describe all the muscles in the tongue and what they are innervated by
* Intrinsic muscles.
* Extrinsic muscles.
* Skeletal muscle innervated by hypoglossal nerve CN XII.
* Genioglossus is the largest muscle of the tongue
93
What is the make up of a taste receptor?
50 - 50 (gustatory cells and supporting/stell cells)
94
Compare and contrast the 3 main salivary glands
Parotid: Secretes serous saliva and parasympathetically innervated by CN IX (Glossopharyngeal)
Submandibular: Secretes mostly mucous and some serous, parasympathetically innervated by CN VII (facial)
Sublingual: Secretes mostly serous and some mucous saliva, parasympathetically innervated by CN VII (facial)
95
Describe the function and innervation pharynx
Muscular passageway for air and food.
* Skeletal muscle innervated by vagus nerve CN X
96
What are the pairs of constrictors in the pharynx?
Superior, middle, inferior
97
Describe the position and innervation oesophagus
* Muscular tube located posterior to trachea (until bifurcation) and anterior to vertebral bodies
* Innervated by vagus nerve CN X and sympathetic supply from T1-T4
98
Describe the structure and innervation of the stomach
Entry: cardiac orifice.
* Exit: pyloric orifice.
* Both surrounded by thickened muscle sphincters to help keep substances inside the stomach.
* Three smooth muscle layers:
* Inner oblique
* Middle circular
* Outer longitudinal
* Innervated by vagus CN X and
sympathetic nerves from T5-T9
(Fundus highest part, also has another part called the body of stomach)
99
What are the different layers of the gastrointestinal wall?
Mucosa = epithelium + lamina propria + muscularis mucosae
* Submucosa = loose & dense connective tissue, glands, lymphoid nodules, blood vessels, nerves
* Muscularis externa = inner circular layer + outer longitudinal layer of smooth muscle
* Adventitia or serosa = connective tissue on external surface
100
What are the sub-components of the small intestine?
Duodenum, jejunum and ileum
101
Describe the duodenum
Proximal part of small intestine, C-shaped, curls around head of pancreas
102
Describe the jejunum
Distal to duodenum, proximal to ileum, upper left quadrant of abdomen
103
Outline the components of the large intestine
Caecum -> Ascending colon -> Hepatic flexure (where liver is) -> Transverse colon -> Splenic flexure -> Descending colon -> Sigmoid flexure -> Sigmoid colon -> Rectum -> Anus
104
What are the specialised structures of the large intestine?
Omental (epiploic) appendices (which are lobules of fat)
Haustra (sacs)
Teniae coli (smooth muscle)
105
What's unique about the rectum and anal canal structurally?
No teniae coli, haustra or omental appendices in rectum & anal canal.
Anal canal surrounded by two sphincters
106
What is the function of the sigmoid flexure?
To take pressure off the rectum
107
Describe the innervation of the two anal sphincters
Internal anal sphincter is smooth muscle under autonomic control (parasympathetic: pelvic splanchnic nerves S2-S4; sympathetic: inferior hypogastric plexus).
External anal sphincter is skeletal muscle under somatic control from the pudendal nerve
108
What is the importance of the pectinate line?
denotes the change from hindgut endoderm to ectoderm of the anal canal
Above and below the lines, different arteries and veins supply
VEINS ABOVE THE PL DRAIN into hepatic portal vein
Veins below the PL drain into internal iliac vein
109
Compare and contrast the foregut, midgut and hindgut
Foregut: From oesophagus to proximal duodenum, blood supply from branches of coeliac trunk
Midgut: From distal duodenum to proximal transverse colon, blood supply branches of superior mesenteric artery
Hindgut: From distal transverse colon to rectum, blood supply from branches of inferior mesenteric artery
110
Outline the hierarchy of organisation in a muscle cell
Muscle fibres/cell:
Myofibrils (surrounded by endo reticulum):
Sarcomeres
111
Describe the structure of a sarcomere (no need to mention the zones)
Centre bit of myosin (thick filament) which is connected to Z-line via titin
Around it is actin (thin filament) which is attached to the Z-line by alpha actinin
112
How many actin molecules are attached to myosin molecules and vice versa?
6 actin molecules surround a myosin molecule
3 myosin molecules surround a actin molecule
113
Describe what the power stroke is
- The energy from ATP puts the myosin head into a high energy state
- Imagine cocking a gun
- That energy can be used to drive movement
- The releasing of the myosin from high energy state to low energy state, as it snaps forward is called the power stroke
- ADP is released from the myosin so it's reading for another power stroke
114
Outline how a muscle cross bridge is formed
1. Myosin binds to the actin
- Myosin head attaches reversibly to high affinity active sites on actin as power stroke occurs
2. Myosin power stroke pulls the actin, which contracts the sarcomere
- ADP is released, which frees the ATP binding site of any molecule
3. ATP binding releases myosin from actin
- Known as conformational change because change from high energy to low energy
4. ATP hydrolysis drives the re-cocking of myosin to high-energy state, but it’s not required for power stroke
115
What are the kinds of muscle contraction
Isometric:
- The muscle stays the same length (imagine holding a bag in the same position)
- In this the elastic components of the muscles stay stretched
Isotonic:
- The tension on the muscle stays constant as the length of the muscle varies
- 2 types:
- Concentric: Muscle length decreases
- Eccentric: Muscle length increases
116
What is active tension?
- Proportional to the number number of actin-myosin crossbridges (how many myosin heads are doing stuff)
- ie: Amount of overlap
- Overlap of myosin heads and actin (sometimes myosin heads will pop off, or power stroke and dont hit actin, sometimes they’ll hit the a-actinin instead etc.)
117
What is the relationship between force, velo and muscle?
Force is inversely proportional to shortening velocity (we lift heavy stuff slow)
Power = Force * Velocity
Force is proportional to number of sarcomeres in parallel (cross sectional area matters more than length of muscle)
118
Compare and contrast PMCA, NCX and SERCA
- All three are pumps that decrease Ca2+ concentration in myoplasm
- PMCA is an ATPase which sits on plasma membrane
- NCX is a antiport transporter that secondary transports Ca2+ with Na+
- SERCA pumps Ca2+ into SR against huge concentration gradient
119
What is the role of calsequestrin?
- Binds to calcium ions and effectively by binding to them, it reduces it’s concentration which allows more calcium to get into the SR
- Furthermore allows SERCA pumps to pump more
120
Describe the important structures related to the sarcoplasmic reticulum
- Network of smooth endoplasmic reticulum which exists around each myofibril
- Within it there are two important structures:
- T Tubules
- Infoldings of the cell membrane which penetrate through the cell and emerge on the other side so action potentials can get in
- Triad
- Where SR and plasma membrane meet
121
How is calcium released so muscular function can occur?
- On the plasma membrane, there is the dihydropyridine receptor
- This lets Ca2+ into muscle from outside the cell
- It’s voltage gated
- It’s long lasting, it stays open for a while
- On the SR, there is the ryanodine receptor
- Release Ca2+ from SR into the myoplasm
- Mechanically gated
- They DHPR receptor above pushes on this gate and physically opens up a path
We say there’s a coupling between the two receptors
122
Why is calcium important for muscle contraction?
On actin, a molecule called tropomyosin blocks myosin from binding to actin. Tropomyosin position is regulated by troponin complex. Ca2+ binds to Tn- C (part of the complex) which causes a conformational change to occur, pushing tropomyosin to move out of the binding site.
123
What is the synapse between a muscle and nerve called?
Neuromuscular junction or motor end plate
124
What kind of neurotransmitter and receptors are involved in neuromuscular junction?
- Motor neurons secrete acetylcholine (ACh)
- It acts on nicotonic ACh receptors when stimulated
- Ligand gated Na+ channels
- Ionotropic (ligand gated Na+ channel)
- Always excitatory
125
Describe a muscle twitch event from going along nerve to contraction to relaxation
Check Notion
126
What is the activation of a muscle twitch called?
Excitation - contraction coupling
127
What is tetanus?
When maximum tension in a muscle occurs (in the disease, it causes involuntary tight muscle spasms)
128
How are skeletal muscle fibers innervated?
One nerve may control many muscle fibres but one muscle fibre only synapses with one nerve (many to one vs 1 to 1)
129
Explain where motor neurons that control skeletal muscle originate from and the pathway they follow
Motor neurons originate from spinal cord (cell bodies in the ventral body). Furthermore, there's a connection to the brain via other nerves to the primary motor cortex.
So the pathway is primary motor cortex (along upper neuron) -> spinal cord -> muscle (along lower neuron)
The nerves are alpha neurons which are heavily myelinated
130
What differentiates reflex from other nervoud processes/commands?
- The intial action in response to a stimulus such as to move is given by centres in the brain, like ‘move leg now’
- However balance, not stumbling etc. is controlled mainly by spinal reflexes
131
Compare and contrast the types of reflexes
(Monosynaptic reflex):
- Simplest kind of reflex
- Single synapse between afferent and efferent neurons
- Can be as simple as just two neurons in series
- One sensory neuron ⇒ synapse in spinal cord ⇒ motor neuron
(Polysynaptic reflex):
- Have two or more synapses
- Reason for this is there might be interneurons between sensory and motor neuron
- Sensory neuron ⇒ interneurons (more synapses in spinal cord) ⇒ motor neuron
132
Describe the structure, position and role of the golgi tendon organs
- Sense change in tension in the muscle
- They’re encapsulated receptors near the tendons of muscles
- They monitor how much tension the tendon is under
- Static, slow adapting
- Dynamic, fast adapting
Transmit via large, fast fibres
133
Describe the structure, position and role of muscle spindles
- Sense change of length in the muscle
- They’re encapsulated intrafusal fibers (they’re inside the muscle)
- They can sense when the muscle has constant tension on it and when the tension is changing
- They’ve got two parts, contractile muscle tissue on the ends and a sensory bit in the middle
- They have mechanically gated gates
- The two contractile parts on the ends are separately innervated to each other (separate nerves)
-These neurons are gamma neurons (slower than alpha neurons)
- Actually the entire spindle is innervated by gamma neurons
134
Describe the myotatic reflex
- Tension in the muscle when you go to catch leads to muscle contraction
- The muscle spindle detects this and it directly synapses with motor neuron (monosynaptic reflex)
- This increases the firing of alpha motor neurons and this contracts the muscle
135
Describe the reverse myotatic reflex
- Tendon tension ⇒ muscle relaxation (GTOs)
- Sensory neuron synapses with interneuron which is inhibitory (glycine)
- Polysynaptic reflex
- INhibits alpha neuron firing which relaxes muscle
- This is a negative feedback loop which prevents damage to the tendon
136
What is a motor unit?
A motor unit is A SINGLE MOTOR NEURON + ALL THE FIBERS IT INNERVATES
137
What is the relationship between myofibres and motor units?
- More myofibres = greater force (strength)**
- More motor units = greater dexterity/fine co-ordination
- This means that you can have lots of strength but no fine co-ordination ( large motor units)
- Or small motor units which have lots of fine co-ordination but minimal strength
138
What are the 3 types of muscle fibers?
- Type 1 (Slow)
- Slow contracting, fatigue resistant
- Type 2a (fast, fatigue resistant)
- Fast contracting, fatigue resistant
- Type 2b (fast, fatiguable)
- Fast contracting, easily fatigued
139
Describe some of the features of motor unit recruitment
Henneman’s Principle:
- Small, slow MU’s have lowest threshold for synaptic activation
- So they will be recruited before fast, big MU's and fibers
- They are recruited sequentially
140
What are some features of cardiac muscle?
- It has a single nucleus in cells
- Striated
- Not as big as skeletal muscle
- Involuntary
141
What are some features of smooth muscle?
- Involuntary
- Small, elongated thin spindle (relaxed)
- Line internal structures (digestive tract, veins/arteries, respiratory passageways)
- Single nucleus in cells
- Non-striated
142
What are the differences between cardiac /smooth muscle and skeletal muscle?
- These two are different from skeletal cause of the nucleus number (many vs 1)
- These are myocytes not myofibres
- Not attached to bones via tendons
- There’s no somatic NMJ so contraction is not voluntary
143
What are some features that cardiac muscle shares with skeletal muscle?
- Still has sacromeres
- Still generates action potentials that go down T-tubules
- Opens DHPRs, ryanodine receptors on sarcoplasmic reticulum
- Calcium releases, binds to troponin, etc etc
- In cardiac muscle, DHPR doesn’t mechanically keep Ryanodine receptors open mechanically
144
Describe the structure of the overall cardiac muscle and how this affects the purpose of cardiac muscle
- The myocytes are joined by intercalated discs
- Gap junctions
- Holes which transmit ions (APs) from cell to cell
- This allows conduction of APs
- Desmosomes
- Super strong junctions which hold myocytes together
145
Describe how the heart contracts and by extension how cardiac muscle contracts
- The heart exhibits autorhythmic
- It can generate it’s own APs without stimulation from nervous system
- Autorhythmic means it can depolarize rhythmically and independently from nervous system
- IN the cardiac myocytes there’s a node called the sinoatrial node
- IN this node there are FUNNY channels which allow Na+ to leak in, it slowly comes in which slowly depolarizes the cell
- When it crosses the threshold we get a action potential that conducts down
- The rate of leaking of Na+ therefore can be said to determine your heart rate
- This leaking of Na+ is called producing a pre potential
- Then due to the existence of gap junctions, the AP is conducted
146
What are the differences in action potentials between cardiac and skeletal muscle?
- Cardiac muscle cells need to have longer action potentials because with nerves, Ap is over in milliseconds but in cardiac cells, we can make heart beat in a few milliseconds
- So have long action potentials
- So in our myocytes we have L-type Ca2+ channels which are SLOW TO OPEN AND CLOSE
- Note there’s also Na+ and K+ channels
- Thus AP become much longer
- By summing all the potentials generated by Na+, K+ and Ca2+, we get a particular shape for excitation of myocytes AND we see there’s a long absolute refractory period
147
What kind of naming convention is used when naming muscle rectus femoris?
Direction of muscle fibers
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Examples of muscles with circular fascicle arrangement
Orbicularis oculi and orbicularis oris
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Muscles with parallel fascicle arrangement
Sartorius and rectus abdominis
150
Examples of muscles with convergent fascicle arrangement
Pectoralis major
151
What is a unipennate muscle and give an example
A muscle which inserts on one side of a tendon (extensor digitorum longus)
152
What is a bipennate muscle and give an example?
Fascicles of muscle insert on opposite sides of tendon. Rectus femoris
153
Give an example of multipennate muscle
Deltoid muscle
154
Where does all the blood from the digestive organs in the abdomen and pelvis drain to?
Hepatic portal vein
