Cells, tissues, muscle, bone Flashcards
What does DNA stand for and what is it?
Deoxyribonucleic acid, it is the blueprint for a living thing. It is a molecule making the shape of a long spiralling ladder, found in the nucleus of a cell in the form of chromosomes.
It tells AMINO ACIDS how to form the perfect protein shape.
It is made up of 4 different types of chemicals (NUCLEOTIDES)
A single strand of DNA is millions of letters long, spending most of it’s life coiled up like a noodle inside a cells nucleus.
What is RNA?
These are special chemicals inside the nucleus that make partial copies of the DNA code (TRANSCRIPTION).
They look a lot like DNA but shorter and only 1 side (of the ladder)
Their small shape and size allows them to fit through tiny pores in the nucleus, into the cytoplasm, and into the ribosome.
What are ribosomes?
They are PROTEIN BUILDING MACHINES.
They read the RNA code 3 letters at a time, suck amino acids out of their surroundings, and stick them together according to RNA code. As the chain grows, it bends, folds and sticks to itself to form a perfectly shaped protein.
Every 3 letters of the code tell the ribosome which of the 20 different kinds of amino acids go next.
Eg. CAA = Glutomine
What is the sequence from DNA?
DNA creates RNA which creates PROTEINS which form LIFE
What are nucleotides?
They are the 4 bases found in DNA.
A - Adenine
G - Guanine
T - Thymine
C - Cytosine
They are arranged in a precise order along the DNA molecule. Each base along one strand of DNA pairs with a base on the other strand in a precise way (known as complementary base pairing)
Adenine pairs with Thymine
Cytosine pairs with Guanine
(The exception here is in mRNA as there is no thymine in RNA, so uracil is added instead to pair with adenine)
The bases run down the middle of the helix and are joined via hydrogen bonds
What is transcription?
It is the process of the DNA template being partially copied to form RNA. It occurs in the nucleus and is catalysed via the enzyme polymerase.
Polymerase unravels the double helix to expose the bases so the code can be read, then produces another strand.
It reads one strand of the dna (the template strand) & uses the strand it has produced to complement the base codes with one change - URACIL is paired with ADENINE instead of thymine.
What is translation?
It is the synthesis of the final protein using information carried on mRNA. It occurs in the cytoplasm, but more specifically the ribosomes. It is the process of a nucleotide sequence being ‘read’ by a ribosome which specifies the amino acid sequence of a protein.
The ribosome slides along the mRNA reading the codons & adding the appropriate amino acid to the growing protein molecule. It carries on until it arrives at a stop codon, where it terminates, synthesises & releases the new protein. Some new proteins are used within the cell itself and some are exported.
Name the 3 types of RNA
mRNA - Messenger RNA. Acts as the messenger between DNA & protein production.
tRNA - Transfer RNA. RNA is generally single stranded, but tRNA folds it into a t shape. It’s responsible for bringing amino acids together during translation to form a peptide chain which becomes a protein. It binds to an amino acid and holds it in place on the ribosome until it is incorporated into a protein.
rRNA - Ribosomal RNA . This is the main component of ribosomes. rRNA combines with special proteins to form ribosomes which then read mRNA to form proteins.
Explain what mitosis is
It is a type of cell division done by most of our body cells, and results in 2 new identical cells with the same number of chromosomes as the original cell.
It is responsible for repair of damage and growth (nails, height etc)
Does NOT create egg or sperm cells.
Where are chromosomes found and how many are they? What are they made out of?
They are found in the nucclei, and there are 46 of them. They are made of DNA and protein.
Summarise the process of mitosis
The initial phase (interphase) is G1 (The cell grows in size and volume), S (Chromosomes replicate making 2 identical copies of DNA. There are now 92 chromatids, but still 46 chromosomes - there is now enough DNA for 2 cells, G2 (further growth and prep for cell division)
Prophase - The replicated chromatin becomes tightly coiled, making it more visable under a microscope. The 46 chromatids pair with the identical chromatid it replicated during interphase, attaching via the centromere creating a double unit chromosome. The mitotic apparatus appears. The centrioles move to opposite ends of the cell and the nuclear envelope dissapears.
Metaphase - The chromatids align in the centre of the spindle and are attached via their centromeres.
Anaphase - The sister chromatids separate along with their centromeres and move to either side of the spindle. The microtubles that form the spindle shorten.
Telophase - The chromosomes are now at 2 opposite ends. The mitotic spindle dissapears and the nuclear envelope develops around each bundle of chromosomes. The chromosomes uncoil, and then cytokinesis occurs. The cytosol, intracellular organelles and plasma membrane split forming 2 identical daughter cells.
Where would you find smooth muscle?
In all the organ systems eg. GI tract, blood vessels
What is an example of a hinge joint and whats its range of motion?
Elbow. There is flexion and extension of the forearm, uni axial movement.
What is an example of a condyloid joint and whats its range of motion?
The wrist. There is flexion, extension, abduction, adduction and circumduction. Bi-axial movement.
What is an example of a ball and socket joint?
The shoulder. Wide range of movement.
What is an example of a saddle joint and what range of motion does it have?
The thumb joint, Bi-axial movement
What are types of synovial joints?
Planar joints
Hinge joints
Pivot joints
Condyloid joints
Saddle joints
Ball & socket joints
What specialised tissue is found on the end of long bones?
Articular Cartilage.
Describe an endocrine gland.
An organ that makes hormones that are released directly into the blood and travel to tissues and organs all over the body. Endocrine glands help control many body functions, including growth and development, metabolism, and fertility. Some examples of endocrine glands are the pituitary, thyroid, and adrenal glands.
What is a dermatome?
They are areas of skin on your body that rely on specific nerve connections on your spine
What is an example of a pivot joint, and what range of motion does it have?
In the neck that allows your head to rotate. It has rotational movement.
What are the islets of Langerhans?
A pancreatic cell that produces hormones (e.g., insulin and glucagon) that are secreted into the bloodstream.
What is the blood brain barrier?
It is a highly selective semipermeable membrane barrier that separates the circulating blood from the brain’s extracellular fluid in the central nervous system (CNS). It selectively allows essential nutrients, oxygen, and certain molecules to enter the brain while preventing the entry of potentially harmful substances, pathogens, and toxins.
What are the 2 types of scwann cells?
Myelinating cells, and nonmyelinating cells.
What are plexuses?
They are networks of interwoven nerve fibers from different spinal nerves.
Examples include the Cervical plexus - provides nerve connections to the head, neck and shoulder
Brachial plexus - located in the neck and shoulders which distributes nerves throughout the chest, shoulders and arms
Lumbar plexus - distributes nerves to back, abdomen, groin, knees, thighs and calves
Sacral plexus - nerves to the pelvis, buttocks, genitals, thighs, calves, feet
What is meiosis?
It’s a process which occurs in the ovaries and testes, producing gametes with half the number of chromosomes (haploid = 23 chromosomes, diploid = two haploids joined).
What is selective permeability?
It is the characteristic which enables the plasma membrane to be selective with which substances enter or leave the cell, therefor regulating the internal composition of the cell.
What is diffusion?
It’s where particles move from a higher concentration to a lower concentration, down a concentration gradient.
What factors effect diffusion?
Temperature, molecular size, speed
What is diffusion through a lipid bilayer?
Non polar hydrophobic molecules such as oxygen, carbon dioxide, carbon dioxide, fatty acids and fat soluble vitamins diffuse freely through a plasma membrane.
Explain diffusion through ion channels
Ion channels are transmembrane proteins that allow small ions to pass through. eg. potassium (K+) and sodium (Na+). These molecules are too hydrophilic to pass through a phospholipid bilayer without a channel. As there are fewer channels in a membrane the process is slightly slower.
Channels can be gated or plugged as the protein changes shape to allow more of fewer ions into or out of a cell.
Ions diffuse down an electrochemical gradient.
What is osmosis?
The passive movement of water from a high concentration to a low concentration.
What is osmotic pressure?
The pressure that develops when two solutions of different concentrations are separated by a semi-permeable membrane, and water molecules move through the membrane to equalize the concentration of solutes on both sides. It is a measure of the force required to stop this flow of water.
The greater the difference in solute concentration between the two solutions, the higher the osmotic pressure. It’s like the “push” that water exerts on the side with higher solute concentration, trying to dilute the more concentrated solution and achieve equilibrium.
What is the function of a ribosome in a cell?
Protein synthesis
What are the three functions of endoplasmic reticulum (rough and smooth)?
Synthesis of fatty acids and steroids
Synthesis of glycoproteins and phospholipids
Intracellular storage of calcium
What is the function of a mitochondrion?
Aerobic cellular respiration and the production of ATP
How many chromosomes does a haploid cell have?
23
What is an example of ciliated simple columnar epithelium?
Uterine tubes
What does an endocrine gland drain into?
Directly into the blood
Name some examples of a serous membrane
Pleura, Peritoneum, Pericardium
What is serous membrane?
The outer lining of organs and body cavities of the abdomen and chest, including the stomach - made of smooth muscle. Secretes serous fluid to allow lubricated sliding movements between opposing surfaces.
What is hemopoiesis?
The production of blood cells
Which part of the long bone contains yellow bone marrow in adults?
Diaphysis (the shaft of central part of a long bone)
What is red bone marrow?
Red bone marrow contains blood stem cells that can become red blood cells, white blood cells, or platelets.
What is yellow bone marrow?
Yellow bone marrow is made mostly of fat and contains stem cells that can become cartilage, fat, or bone cells.
What movement does the levator palebrae superioris muscle create?
Raises the eyelid
What is ossification?
Bone formation
Which proteins are involved in muscle contraction?
Actin, Myosin and Troponin
What do fibroblasts do?
Manufacture collagen and elastin fibres - contributing to the formation of connective tissue.
What three things effect bone growth?
Minerals, hormones and vitamins
What is facilitated diffusion?
It’s the process by which solutes that are two polar or too highly charges to pass through passively, bind to a specific transporter on one side of the membrane and are released on the other side (hitching a lift)
Still a passive process, determined by a concentration gradient.
What is active transport?
It is where transporter proteins (PUMPS) move solutes across a membrane against the concentration gradient and ENERGY (ATP) is required.
Ions that are moved in this way are Na+, K+, amino acids
How does a sodium/potassium pump work and which cells have it?
All cells possess this pump.
Sodium and potassium diffuse down their concentration gradient which results in higher potassium levels on the outside and higher sodium levels on the inside. The pump forces the ions to move from an area of low concentration to an area of high concentration using ATP. It moves soidum ions out of the cell, and potassium ions into the cell to enable to keep the unequal concentrations on either side of the plasma membrane.
Nerve impulses use this electrical gradient.
Transport in vesicles
This is an active process as it requires ATP. Substances are either transported into or out of a cell in a vesicle.
What is phagocytosis?
It translates to ‘cell eating’. It brings in larger particles into a cell such as cell fragments, foreign material and microbes, into a vacuole and is processed in the same way as pinocytosis.
What is pinocytosis?
It translates to ‘cell drinking’. the cell membrane wraps around liquid and larger particles that are outside of the cell, and brings them inside the cell. The membrane breaks off and it becomes a vacuole. Lysosome then binds to the vacuole membrane and releases enzymes to digest the contents, then the waste materials are released back through the membrane in a phase known as exocytosis.
What are the functions of the plasma membrane?
Protecting the contents of the cell
Communicating with other cells
Regulating the flow of materials in and out of the cell
Maintains the appropriate environment within the cell
What is the lipid bilayer?
The lipid bilayer is a type of membrane that separates the cell from the environment and is made of two layers of phospholipids. Also known as the phospholipid bilayer, the cell membrane surrounds the cell and forms a flexible barrier that allows the cell to be separate from the extracellular space.
It is composed of two back to back layers of lipids:
Phospholipids
Cholesterol
Glycolipids
This layer occurs because the lipids are amphipathic (polar and non polar regions). The fatty acid tails (non-polar areas) are in the centre of the bilayer, away from the water in the cytosol and extracellular fluid.
What are membrane proteins and whats their function?
They provide channels for non-lipid soluble substances and electrolytes as they pass all the way through the membrane. They also act as receptors to hormones and c hemical messengers. Some are enzymes.
Some have branches that carbohydrate molecules attach to outside of the cell, giving the cell it’s immunological identity.
What is the cytoplasm?
The cells contents (including the cytosol and organelles, it EXCLUDES the nucleus).
It serves as a medium for important reactions and molecule transport.
What is cytosol?
The watery fluid inside a cell which suspends organelles.
It gives the cell its shape and structure, and is resposible for metabolic reactions eg. glycolosis
What are organelles?
They are the ‘small organs’ inside the cell.
Includes the nucleus, mitochondria, ribosomes, endoplasmic reticulum, golgi apparatus, lysosomes and cytoskeleton.
They are enclosed within their own membrane in the cytosol.
They all have individualised and highly specialised functions.
What is the cytoskeleton
A network of tiny protein fibers.
It’s an internal support system for the cell.
Centrosome
This is made up of a pair of centrioles (small clusters of microtubules). Plays an important part in cell division.
Cilia and flagella
Cilia is microscopic hair like projections containing microtubules that lie along the borders of some cells. They beat in unison to move substances along the surface.
Flagella are single, long, whip like projections containing microtubules which form the tails of spermatozoa.
Golgi complex
Present in all cells but larger in ones that synthesise and export proteins. Made of stacks of closely folded flattened membranous sacs.
Proteins move from the endoplasmic reticulum to the golgi complex where they are packaged into membrane bound vesicles. The vesicles are stored, and when needed get expelled using exocytosis.
Lysosome
Small membranous vesicles pinched off from the golgi complex. They contain enzymes involved in breaking down fragments of organelles and large molecules inside the cell into smaller particles that can then be recycled or exported.
Mitochondrion
Membraneous sausage-shaped structures in the cytoplasm.
The powerhouse of the cell.
Produces energy in the form of ATP through cellular respiration.
Nucleus
All body cells have this expect for mature red blood cells.
Found in the nuclear envelope.
Contains the bodys genetic material in the form of DNA, also contains RNA.
Give an example of a positive feedback system
Childbirth.
The release of oxytocin creates a hormonal stimulation of contractions in the uterus - this moves the babies head into the cervix, stimulates stretch receptors within the cervix which triggers the release of more oxytocin. This strengthens contractions and maintains the state of labour. Once the baby is born, the uterus and cervix are no longer stimulates and so the release of oxytocin is stopped.
Give an example of a negative feedback system.
Core body temperature.
If the body temperature falls below 37 degrees, specialised temperature sensitive nerve endings found in the skin pick up on this and send a notification to the hypothalamus in the brain. The hypothalamus issues the effectors, activating mechanisms to raise the body’s temperature (stimulation of skeletal muscles to induce shivering, narrowing of the blood vessels to reduce blood flow to and heat loss from the peripheries, and of course behavioural changes, e.g. putting more clothes on). When the body temperature rises to its normal range, the temperature-sensitive nerve endings are no longer stimulated and their signals to the hypothalamus stop.
Location and function of simple squamous epithelium
Heart (endocardium), blood vessels & lymph vessels
Made of a single layer of flattened cells, they fit closely together like paving stones forming a thin & smooth membrane where diffusion easily occurs.
Location and function of simple cuboidal epithelium
The walls of the kidney tubules some glands such as the thyroid.
Cube-shaped cells fitting closely together & lying on a basement membrane. Involved in secretion, absorption and excretion.
Location & function of non ciliated simple columnar epithelium
Found in many organs, the lining of the stomach & the lining of the small intestine.
It’s a single layer of tall, thin cells on a basement membrane.
Location & function of ciliated simple epithelium
Trachea and uterine tubes.
Ova are propelled along towards the uterus in the uterine tubes by cilia.
Location & function of stratified squamous epithelium
Outer layers of skin, mouth, vagina
Protects against drying out, abrasion, infection
Transitional epithelium location & function
Urinary tracts including bladder
Made up of several layers of pear shaped cells, allows for stretching as bladder fills.
What is the function of an exocrine gland?
They secrete substances onto a surface or into ducts. EG. sweat, saliva, digestive enzymes.
What are three types of fibres found in connective tissues?
Collagen, elastic and reticular fibres
What cells are involved in connective tissue?
Fibroblasts
Macrophages
Plasma cells
Mast cells
Adipocytes
White blood cells
Location and function of areolar connective tissue
Almost every part of the body.
Provides elasticity and tensile strength. Connects and supports other tissues (under the skin, between muscles).
Location and function of adipose tissue
There is white and brown. White is found in the kidneys and the eyeballs, between muscle fibres and under the skin. Brown is found in the upper chest an neck areas.
White is a thermal insulator and energy store.
Brown has more mitochondria and generates more heat than white adipose tissue - essential in keeping newborn babies warm.
Location of reticular connective tissue
Lymph nodes and lymphatic organs.
Location & function of dense connective tissue
Found in tendons, ligaments, the respiratory tract, blood vessel walls
They stabilize & support surrounding tissues and organs
Location & function of elastic connective tissue
In organs where strecthing or alteration of shape is required.
To allow extension and recoil
Hyaline cartilage location & function
On the ends of long bones that form joints, the costal cartilages that attach the ribs to the sternum
Provides flexibility, support and smooth surfaces
Fibrocartilage location & function
Found as the pads between the body’s vertebrae
A tough slightly flexible supporting tissue
Elastic fibrocartilage location & function
The epiglottis
Provides support and maintains the shape
Location and function of bone in relation to connective tissue
They are surrounded by a matrix of collagen fibres, strengthed by calcium and phosphate. They bring strength and rigidity to the human body.
What does an epithelial membrane consist of? (2 layers)
An epithelial layer and an underlying connective tissue layer
What are the differences between mucous and serous membranes?
Mucous membranes = line exposed surfaces such as digestive and respiratory tracts, they secrete mucous for protection. Made up of stratified or simple columnar epithelium. Defend against external threats, aid nutrient absorption.
Serous membranes = Found in closed body cavities like the thoracic and abdominal cavities, produce a lubrication serous fluid. Made up of simple squamous epithelium. Reduce friction during organ movements.
How is tissue repair carried out?
New cells form via mitosis from the stroma, or the parenchyma.
Latin name for Head region
Cephalic
Latin name for neck region
Cervical
Latin name for armpit region
Axillary
Latin name for arm region
Brachial
Latin name for front of elbow region
Antecubital
Latin name for Forearm region
Antebrachial
Latin name for wrist region
Carpal
Latin name for Palm region
Palmar
Latin name for fingers region
digital
Latin name for thigh region
femoral
Latin name for anterior surface of of knee
Patellar
Latin name for leg
crural
Latin name for ankle region
Tarsal
Latin name for foot region
Pedal
Latin name for toes
digital
Latin name for Chest region
Thoracic
Pubis
Pubic
Hands
Manhs
Groin
Inguinal
Hip
Coxal
Naval
Umbillical
Breast
mammary
Chin
Mental
Mouth
Oral
Nose
Nasal
Cheek
buccal
Ear
Otic
Eye
Orbital
Forehead
Frontal
Shoulder
Acromial
Shoulder blade
Scapular
Spinal collumn
Vertebral
Between hips
Sacral
Buttock
Gluteal
Hollow behind knee
Popliteal
Calf
Sural
Sole of foot
Plantar
Heel
Calcaneal
Directional term - Intermediate
Between 2 structures (eg. the knee is intermediate between the foot and hip)
Directional term - Ipsilateral
On the same side of the body
Directional term - Contralateral
On opposite sides of the body
Directional term - Proximal
The closest point to the attachment of a limb
What are the functions of bone and the skeletal system?
Support
Protection
Assistance in movement
Mineral homeostasis - minerals are released into the blood to maintain homeostasis
Blood cell production
Triglyceride storage (in yellow bone marrow)
Osteoblasts
Are bone-forming cells. They deposit both inorganic salts and esteoid in bone tissue.
They are present at sites where bone is growing, repairing or remodelling
Osteocytes
These are mature bone cells that do not divide.
They monitor and maintain bone tissue.
Osteoclasts
These cells break down bone, releasing calcium and phosphate. They are giant cells with upto 50 nuclei. Found where bone is growing, repairing, remodelling.
What is compact bone?
It is the strongest form of bone
Forms bulk diaphysis of long bones
Found in all bones throughout the human body. Compact bone forms the hard, dense outer covering of bones,
Provides protection and support for movement
*Blood, lymph vessels and nerves penetrate compact bone through perforating canals
Spongy bone
Isn’t actually spongy
It forms short, flat and irregular bone shapes
Forms epiphyses of long bones
Provides support and protection bone marrow
Ossification
is bone formation.
There are 2 tyes: intramembranous - where bone forms within mesenchyme in sheet like layers
endochondral ossification where bones form with hyaline cartilage
Bone growth in length
Occurs at the epiphyseal plate up until 18 years old in females and upto 21 years old in males. At this point cartilage cells at the epiphyseal plate stop dividing and become bone.
Bone growth in thickness
This is through a process called appositional growth.
Osteoblasts deposit new bone tissue on the external surface. Simultaneously osteoclasts remove old or damaged bone tissue from the inner layer (endosteum). It is these opposing processes which create outward expansion of bone.
What are the 3 main factors affecting bone growth?
Hormones, exercise and diet
What are the 3 types of muscular tissue?
Skeletal muscle tissue
Cardiac muscle tissue
Smooth muscle tissue
Describe skeletal muscle tissue
It moves the bones of the skeleton
Is striated
Is voluntary through part of the somatic nervous system
Describe cardiac muscle tissue
Forms the heart wall
Is striated
Involuntary
Describe smooth muscle tissue
Forms the walls of hollow internal structures (eg blood vessels, abdominal organs)
Nonstriated
Involuntary
What are the four main functions of muscular tissue?
MOVEMENT - Muscles enable voluntary and involuntary movements of the body. They allow for conscious movements such as walking etc. Smooth muscle contributes to involuntary movement in internal organs like the digestive system.
SUPPORT - Muscles provide support to the body and help maintain posture. Core muscles play a key role in stabilising the spine.
HEAT - Muscular contraction releases energy in the form of heat, this contributes to the bodies temp regulation. Especially important in cold environments.
JOINT STABILITY - Muscles stabalize joints by surrounding and supporting them. The contraction of muscles around joints help prevent excessive movement - reduced risk of injuries.
What is a sarcolemma
The cell membrane of a muscle fiber (cell). It surrounds and encases the muscle cell, plays a crucial role in transmitting signals for muscle contraction.
What is a sarcoplasm
The cytoplasm of a muscle cell. It contains organelles including myofibrils, glycogen and myoglobin.
What is myoglobin
A protein found inside muscle cells that binds with oxygen, facilitating its storage and release. It plays a vital role in providing oxygen to muscle tissues during periods of increased activity.
What are myofibrils
They are long, cylindrical structures within muscle cells composed of repeating sarcomeres. They contain contractile units of muscle, namely actin and myosin filaments and are responsible for muscle contraction.
What is the sarcoplasmic reticulum
Specialised endoplasmic reticulum found in muscle cells. It stores and releases calcium ions, which are essential for muscle contraction. The release of calcium triggers the sliding of actin and myosin filaments during muscle contraction.
What are filaments
They are the thin protein strands (actin & myosin) that make up the myofibrils. During muscle contraction these filaments slide past eachother, causing the muscle to shorten.
What is the sarcomere
It is the structural and functional unit of a myofibril. It is the segment of myofibril between 2 Z-lines. The interaction of actin and myosin filaments within the sarcomere leads to muscle contraction.
Myofibrils are built from which 3 kind of proteins?
Contractile proteins - generate force during contraction
Regulatory proteins - which help switch contraction on and off
Structural proteins - keep filaments aligned, give elasticity and extensibility, links the myofibril to the sarcolemma and extracellular matrix
What is Excitation-contraction coupling?
It is the process that links the electrical signal (action potential) in a muscle cell to the actual muscle contraction:
- Nerve signals stimulate the muscle cell membrane (sarcolemma), leading to the generation of an action potential.
- Action potential travels along the sarcolemma into the Ttubules (these are deep into the muscle cell)
- T-tubules signal sarcoplasmic reticulum to release stored calcium ions into the cytoplasm.
- Calcium binds to troponin (bike lock). This causes a change in troponin, which moves tropomyosin (bike chain) away from the myosin-binding sites on the actin filaments
- Now the binding sites are exposed, myosin heads on the thick filaments can attach to actin, forming cross-bridges.
- ATP powers the movement of myosin heads, leading to the sliding of actin and myosin filaments past eachother. This results in muscle contraction.
- Calcium is pumped back into the SR, troponin returns to it’s original conformation. Tropomyosin covers the myosin-binding sites on actin, leading to muscle relaxation.
What is the neuromuscular juntion?
It is the synapse between the somatic motor neuron and the skeletal muscle fibre. It is where muscle action potentials arise. the action potential jumps the gap (synaptic cleft). Neurotransmitters are used to communicate between the two cells.
Describe the process of what happens at the NMJ
It begins with the arrival of an action potential (nerve impulse) at the motor neurons axon terminal.
The action potential triggers the opening of voltage-gated calcium channels in the neurons axon terminal. The influx of calcium stimulates the release of acetylcholine from synaptic vesicles into the synaptic cleft.
Acetylcholine diffuses across the synaptic cleft and binds to the nicotinic acetylcholine receptors on the sarcolemma of the muscle fibre.
ACh binding to receptors causes the opening of ligandgated sodium channels on the muscle cell membrane. The influx of sodium generates endplate potential (a depolarization of the muscle cell membrane).
The EPP triggers an action potential that moves along the sarcolemma into the T-tubules.
The action potential signals the SR to release calcium ions into the cytiplasm of the muscle cell.
Calcium binds to troponin, initiating the sliding actin and myosin filaments - leading to muscle contraction.
Acetylcholinesterase (an enzyme in the synaptic cleft) breaks down ACh, terminating the signal and preventing continuous muscle stimulation.
How do muscles produce ATP?
Aerobic respiration = mitochondria within muscle cells utilize oxygen to metabolize glucose and fatty acids, producing ATP
Anaerobic processes = glycolysis breaks down glucose to generate ATP without oxygen
What is muscle fatigue?
Where muscles work at a level that exceeds the supply of oxygen and fuel such as glucose. The muscle response decreases with fatigue.
What is muscle tone?
A sustained partial muscle contraction that allows maintenance of posture without fatiguing the muscles involved. eg. keeping the head upright.
Summarise the processes of mastication and deglutition.
Chewing and swallowing.
Mastication = physical breakdown of food
Deglutition = Oral buccal phase, pharyngeal phase, oesophageal phase.
How are alveoli suited to gas exchange?
They are single-cell walled, great for facilitating diffusion
They have elastic properties
They are fluid-lined which facilitates gases exchange as well as assisting with the elastic recall
Alveoli have a large surface area and a close association with blood vessels
Compare pulmonary and systemic circulation
Pulmonary = carries deoxygenated blood from the heart to the lungs, oxygenated blood from the lungs to the heart.
Systemic = Carries oxygenated blood from the heart to the body, then deoxygenated blood back to the heart.
Pulmonary artery - the only artery that carries deoxygenated blood.
Pulmonary vein - the only vein that carries oxygenated blood.
2 Systems are similar = Both components of double circulation, both occur in many mammals, they are both closed circuit systems, functions are that respiratory gases nutrients and metabolic wastes get to their final destinations, both comprised of arteries and veins.
Describe function and structure of lymph nodes
Small bean-shaped masses of lymphoid tissue, enclosed by a capsule.
Could draw the difference between lymph nodes and lymph nodules.
They filter blood
They provide areas where antigens can be trapped and exposed to the immune system for destruction or education.
Found in the junctions of major lymphatic vessels (neck, groin, armpits)
Capsule and cortex - 2 regions of a lymph node.
Lymph drains into the lymph vessels but they can also drain from one node to another.
