Anatomy, Histology & Physiology (Week 19) Flashcards
(27 cards)
What is the Integumentary System?
The skin and its associated accessory structures and organs make up the integumentary system.
What are the two main tissues of the skin?
Epithelial Tissue
Connective Tissue
What are the two distinct layers of the skin?
- Epidermis (composed of stratified squamous epithelium)
- Dermis (Composed of connective tissue, nervous tissue and blood)
What are the functions of the skin?
- Protection and touch
- Skin temperature regulation
- Temperature synthesis of vitamin D
- Wound healing
- Injury Excretion and absorption
What are the accessory structures of skin?
Nails
Hair follicles
Glands
Functions of nails
- Protective coverings
- Consists of a nail plate that covers nail bed
- Nail matrix contains stem cells
Function of Hair follicles
- Contains the hair root, which can extend into subcutaneous layer
- Sebaceous glands
- Arrector pili muscle
- Sweat glands
- Nerve endings
Function of glands
- Endocrine glands: Secrete substances into the interstitial fluid and bloodstream (e.g. hormones
- Exocrine glands: Secretes substances into ducts and onto the surface (e.g. sweat, saliva, mucus, milk)
Functions of Muscles
- Movement
- Stability
- Regulating organ volumes
- Movement of substances
- Heat production
What are the properties of muscles?
- Excitability: Respond to chemicals released from nerve cells
- Conductivity: Ability to propagate electrical signals over membrane
- Contractibility: Ability to contract and generate force
- Extensibility: Ability to be stretched without damaging the tissue
- Elasticity: Ability to return to original shape after being stretched
What are the three types of muscle tissue?
- Skeletal muscle tissue: Attached to bones of skeletons
- Smooth muscle tissue: Forms the walls of hollow internal tissues
- Cardiac muscle tissue: Forms the wall of the heart
Summarise Skeletal Muscle Tissue
Typically attached to bones, skin or fascia. Conscious control of voluntary muscle tissue.
Cells are long and threadlike with alternate light and dark cross-markings called striations. Cells are multinucleated.
Skeletal muscles move the head, trunk and limbs
Summarise Smooth Muscle Tissue
Shorter than skeletal muscle cells are spindle shaped and do not have striations. They are also mononucleated.
They are found in walls of hollow internal organs (stomach, intestines, urinary bladder, blood vessels)
Involuntary
Summarise Cardiac Muscle
Found only in heart and makes up majority of it. They are striated and branched, joining end to end and form complex networks.
Cells are mononucleated and involuntary.
What is a Sarcomere and how does it contribute to muscle contraction?
It is a functional unit of muscle contraction. Contains alternating thick (myosin) and thin (actin) filaments.
During concentration, these filaments slide past one another, shortening sarcomere and entire muscle fibre.
What are the main protein filaments in a myofibril, and what are their functions?
Myosin (Thick filaments): Composed of multiple myosin molecules, each with a globular head that binds to actin during contraction
Actin (Thin filaments): Twisted double strands that contain binding sites for myosin heads
Troponin and Tropomyosin: Regulatory proteins on the thin filaments that control myosin binding by responding to calcium levels
What happens when calcium (Ca2+) levels increase in the muscle fibre?
When Ca2+ increases, it binds to troponin, causing tropomyosin to shift and expose the binding sites on actin. This allows myosin heads to attach, leading to muscle contraction.
Describe the steps of the Sliding Filament Model of muscle contraction
- Calcium ions (Ca2+) bind to troponin, exposing actin’s binding sites
- Myosin heads attach to actin, forming cross-bridges
- Power stroke: Myosin heads pivot, pulling actin filaments toward the sarcomere centre.
- ATP binds to myosin, causing it to detach from actin.
- ATP is hydrolysed, resetting the myosin heads to their original position
- Cycle repeats as long as Ca2+ and ATP are present.
What is the neuromuscular junction (NMJ), and why is it important?
The NMJ is the synapse between a motor neurone and a skeletal muscle fibre. It is essential for initiating muscle contraction. When a nerve impulse reaches the NMJ, it triggers the release of Acetylcholine (ACh), which binds to receptors on the muscle fibre, leading to an electrical impulse (action potential) that starts contraction.
What are the main components of the NMJ?
- Synaptic end bulbs: Swollen ends of neuron containing Acetylcholine vesicles.
- Synaptic Cleft: Gaps between neuron and muscle fibre
- The folded muscle membrane with Acetylcholine receptors.
What happens when Acetylcholine (ACh) is released at the NMJ?
- Acetylcholine is released from synaptic vesicles in the neuron.
- Acetylcholine diffuses across the Synaptic Cleft
- Acetylcholine binds to its receptors on the motor end plate
- Triggers an electrical impulse (action potential) in the muscle fibre, leading to contraction.
- Acetylcholine is broken down by Acetylcholinesterase (AChE) to stop stimulation.
What are the 3 main muscle attachment points?
Origin: Fixed attachment (bone that does not move)
Insertion: Moveable end, pulled toward the origin during contraction
Belly: Fleshy part of muscle between origin and insertion
How do skeletal muscles create movement?
Skeletal muscles act as levers that pull on bones at joints. Movement depends on:
- Rigid bar (bone)
- Fulcrum (joint/pivot point)
- Effort (Muscle force applied to move the bone)
What are the four types of muscle roles in movement?
- Agonist (prime mover): Main muscle responsible for movement (e.g biceps in arm flexion)
- Antagonist: Opposes the agonist (e.g triceps in arm flexion)
- Synergist: Assists the agonist by reducing unwanted movement
- Fixator: Stabilises origin of agonist
