Module 4 B Flashcards
Give 2 examples of cell specialisation in the human body
endothelial cells - form walls of blood vessels
muscle cells - cause peristaltic contractions
Key stages of animal embryogenesis
egg (cleavage - series of rapid cell divisions) –> bastula (gastrulation - cells move inwards to generate the germ layers) –> gastrula (organogenesis - formation of the tissues & organs of the body - neurulation) –> tail-bud stage –> differentiation commences & electrically active neural cells / muscles arise
Gastrulation & establishment of the germ layers
- Bastula (flattening)
- Cells at the base of the bastula begin to change shape
- Inward bulge formed by cells changing shape. Cells separate from outer layer & move inwards - form the mesoderm.
- Cells in the invagination form the endoderm layer.
- Endodermal cells extend, flatten, & undergo rearrangement to form a long thin tube - the gut
- Gastrula is formed. Future sites for the mouth & anus determined
blastopore = future site for anus
different types of tissue arise from the germ layers
- endoderm, mesoderm, ectoderm
Ectoderm
gives rise to external surfaces (e.g. skin) & the nervous system
Mesoderm
gives rise to many internal tissues like muscles, blood vessels, & other connective tissues
Endoderm
gives rise to the cells that line the alimentary canal & the various organs that branch off from it such as the lung, pancreas, & liver
Triploblastic animals
animals with 3 germ layers are called triploblast (most animals)
Diploblastic animals
animals lacking a mesoderm have 2 germ layers & include cnidarians like jellyfish & hydra (only have endoderm & ectoderm)
A stem cell division produces. . .
a new stem cell and a daughter cell that
can subsequently differentiate into other cell types
Organogenesis
involves several morphogenic processes - cell movement, cell adhesion, changes in cell shape
– interactions B/W the germ layers
Organogenesis is the process of formation of organs from three germ layers
Cell potency
ability of cell to give rise to other cell types
Describe epithelial tissue
2-D sheets of cells that cover the body surface internal cavities, & internal tubes such as the alimentary canal
Function of epithelial tissue
provide a barrier function b/w the body & outside world & b/w compartments of the body
endothelia –> epithelial tissues that line blood vessels & are of mesodermal origin
Epithelial cell features
apico-basally polarized
cell-cell junctions
tight junctions
– prevent passage of
small molecules between cells
* adherens junctions and
desmosomes provide mechanical
support
* Gap junctions allow cell cell
communication
cell-matrix junctions
attach epithelial cells to the
underlying extracellular matrix
(ECM) (called the basal lamina)
Functions of epithelia
glands – secretion of hormones, enzymes, sweat
intestine – absorption of nutrients
skin – protection from mechanical damage, heat loss, microbes, & water loss
airways – beating of cilia to keep airways clear of mucus & dirt
Connective tissue
support & connect other tissues
- usually consist of a few cells that exist in & contribute to an EXTRA-CELLULAR MATRIC (ECM)
ECM
- an interlocking mesh of fibrous proteins within some ground material, usually liquid but solid in the case of bone
- embedded proteins like collagen & elastin are secreted by cells, often by the cells within the matrix
Examples of connective tissue functions
tendons – strong connection b/w muscles & bones
bone – rigid support & protection of delicate tissues
adipose – storage & metabolism of fats
blood – transport of oxygen & carbon dioxide, nutrients, immune cells
cartilage – rubbery / flexible; shock-absorbing; friction reducing
Nervous tissue
- processing info
- gather info about the external & internal env.
- control physiology & behaviour of body
NEUTRONS TRANSMIT ELECTRICAL SIGNALS CALLED ACTION POTENTIALS
GLIAL CELLS PROVIDE MECHANICAL & NUTRITIONAL SUPPORT FOR NEURONS
- do NOT generate action potentials (e.g. Schwann cell)
3 types of neurons
- sensory neurons
- interneurons
- motorneurons
sensory neurons
generate electrical signals based on dif. stimuli (e.g. touch receptors) – output to neurons
interneurons
take input from neurons - output to other neurons
motorneurons
take input from neurons - output to muscles
examples of sensory neurons
- pressure receptors in skin
- stretch receptors in muscle
- olfactory receptors in nose
- photoreceptors in eye
Muscular tissue (3 types) – generating contractile force
- skeletal
- cardiac
- smooth
skeletal muscle
connects to the skeleton & generates voluntary movements of the body
cardiac muscle
contraction of the heart under involuntary control
what causes muscle contraction?
caused by an ATP-dependent motor protein comprised of myosin filaments pulling on actin filaments - contraction is activated by electrical signals
smooth muscle
surrounds internal organs - mainly under involuntary control
Integumentary system
provides a barrier to outside environment (skin)
Respiratory system
gaseous exchange
gastrointestinal system
digestion of food, absorption of nutrients, & removal of waste
urinary system
elimination of waste, regulating blood volume & pressure
lymphatic system
controlling bodily fluids & movement of immune cells
reproductive system
involved in propagation
skeletal system
provides support for the body
muscular system
enables locomotion & other bodily movements
nervous system
control & coordination of various bodily activities & responses to the env.
endocrine system
secretes hormones that regulate metabolism, growth, & development
cardiovascular system
movement of blood around body
Example of organ systems working together
Endocrine system: secretes hormones into blood
Digestive system: pass nutrients & water into blood & hormones
Respiratory system: oxygenates blood & removes CO2
Urinary system: removes nitrogenous waste from blood
Stimulus-response model
- receptor detects a change AWAY from the desired equilibrium value & signals to a control centre
- control centre receives & processes this info & communicates to an effector
- an effector creates a response that opposes the effect of the stimulus
–> negative feedback
How do cells communicate with other cells?
- cytoplasmic connections (e.g. gap junctions in animals, plasmodesmata in plants)
- local signalling –> autocrine; juxtacrine; paracrine
- hormones in blood have long-distance, systemic effects
- in animals, cells can generate electrical signals (action potentials)
3 main groups of animal hormones
- steroid hormones (testosterone)
- amine hormones (epinephrine)
- protein hormones (insulin)
Hydrophilic hormones
- secreted from cell via exocytosis
- binds to cell-surface membrane receptors
lipophilic hormones
- diffuses through membrane
- binds hydrophilic transport proteins
lipophilic
tending to combine with or dissolve in lipids or fats.
consequences of low blood sugar (hypoglycemia)
seizures
loss of consciousness
consequences of high blood sugar levels (hyperglycemia)
damages cells, causing heart disease, stroke, kidney disease, vision impairment
Insulin causes liver cells to store glucose as glycogen
liver cells express the insulin receptor
insulin binding activates the receptor which has 2 effects:
1. Increases number of glucose transporters in
the membrane (yellow)
2. Activates an enzyme (glycogen synthase) that
converts glucose to glycogen
so blood glucose goes down
glucagon causes glucose to be released
Liver cells also express the Glucagon G-
protein coupled receptor. Glucagon activating
its receptor has two effects:
1. Activation of glycogen phosphorylase
2. Inactivation of glycogen
This leads to breakdown of glycagon into
glucose molecules
glucose levels go up
functions of plant hormones
growth & development
seed dormancy
defense against herbivores
stress response
Which plant hormones promote stem growth?
auxin, brassinosteroids, & gibberellins
Abscisic acid promotes seed dormancy,
gibberellins promote seed germination
How do auxin & gibberellin act?
- In the absence of the hormone, cellular responses are kept inactive by a repressor
- The hormone binds to a receptor, allowing the complex to enter the nucleus
- The complex binds to the repressor, stimulating the addition of a protein degradation signal
- The repressor is degraded, triggering a cellular response to the hormone
under dry conditions in plants. . .
Abscisic acid (ABA) produced in roots and leaves
ABA causes guard cells to become flaccid and stomata close
guard cells have high water potential & low turgor pressure - water stress
How does ACA stimulate a drought response?
prolonged ABA exposure activates a signalling pathway - triggers expression of genes that mitigate water stress
- increased root growth
- reduced shoot growth
- expression of proteins that stabilize cellular content
What is the Ferguson reflex?
is a positive feedback loop that ensures that, once contractions begin, they build in strength
until the baby is delivered.
How does ferguson reflex work?
- pituitary gland stimulated to release oxytocin
- oxytocin causes uterus to contract
- baby pushing against cervix activates stretch receptor neurons
- sensory neurons send signal to the brain (hypothalamus)
Why do some animals lack a circulatory system?
bc their cells are all a short distance from the env - (e.g. animal is small, flat, hollow, porous etc)
Animal circulatory system needed for:
- transportation of substances
- transportation of heat
- transmission of force
Animal circulatory systems need what?
- a muscular pump
- a circulating fluid
- a system of tubular vessels that form a circuit
Distinguish between open circulatory system & closed circulatory system
Open circulatory system: circulating fluid empties OUT into the body cavity
Fluid in circulatory system is SAME as that in body cavity (hemolymph)
Closed circulatory system: circulating fluid is contained within a network of vessels
Circulatory fluid is separate from interstitial fluid
Circulatory fluid is called blood plasma
e.g. of animals w/ open systems
arthropods (insects, crustaceans, e.g. lobster, most molluscs)
e.g. of animals w/ closed systems
worms, vertebrates (fish, birds, etc.) → have high metabolic activity
Advantages of closed circulatory system:
- Fluid flow is MORE rapid in closed system – faster metabolism
- Control of flow – direct flow to where it is needed
- Specialized content of blood plasma – retained cells / large molecules e.g. proteins
circulation for fish
4-chambered heart
Gas exchange with water
Single circuit circulatory system
Low blood pressure in vessels leading to body (slow flow)
valves ensure 1 one flow
The Windkessel effect - dampening large fluctuations in fish
Elasticity of the bulbus arteriosus dampens the large fluctuation of pressure from the ventricles (in fish)
Human major arteries like the aorta serve same function
Characteristics of circulatory systems in vertebrates
3 chambered heart
Gas exchange w/ air
2 circuit circulatory system
Pulmonary & systemic circuits partially separated - mixed blood
Characteristics of circulatory system in birds/mammals
4-chambered heart
Gas exchange w/ air
2 circuit circulatory system
Low blood pressure in vessels leading to lungs
High blood pressure in vessels leading to body (rapid flow)
Evolution of vertebrate circulatory systems
Increased separation b/w blood flowing to the gas-exchange organs from blood that flows to body
- crocodilian right ventricle can pump to both pulmonary or systemic circuits - when crocodile is UNDERWATER, vessels in PULMONARY CIRCUIT constrict, increasing resistance
Human circulatory system characteristics
4-chambered heart
Pulmonary & systemic circuits are separate
Different pressure in pulmonary & systemic circuit
Organs supplied in parallel, but liver takes blood directly from intestine
Walls of right ventricle are thinner than walls of left ventricle - because left ventricle must push out blood to body so higher pressure
Role of pacemaker
Spontaneous generation of AP (action potential) by pacemaker cells at the sinoatrial node
Electrical signal spread across the atria via gap junctions resulting in coordinated contraction
Signal causes activation of the atrioventricular node
Electrical signal passes down modified cardiac fibers (Pukinje fibers)
Electrical signal spreads across the ventricles via gap junctions resulting in coordinated contraction
NOTE: THE CELLS OF THE sinoatrial node, atrioventricular node, & Pukinje fibers are all types of cardiac muscle cells
Systole
ventricles contract, atria relax
Diastole
ventricles relax, atria contract
What powers blood flow through veins?
Blood flow through veins is powered by skeletal muscles & gravity
Distinguish b/w arteries, veins & capillaries
Arteries: thick, elastic, & muscular - can support high pressures of blood leaving heart
Veins: have valves to ensure 1-way flow of blood returning to heart under low pressure
Capillaries: have very thin walls (1 cell thick) to allow diffusion
Give a brief overview of gas exchange in the lungs
Air enters the lung through an arteriole & fills alveoli
Alveoli are covered by a network of fine capillary
Diffusion across thin alveoli & endothelial cells
Incoming blood has low concentration of O2 which diffuses in, & high concentration of CO2 which diffuses out
water potential =
osmotic pressure + blood pressure
Outline Starling’s Model
Pressure potential goes down from 40 mm Hg to 16 mm Hg from artery to vein
Osmotic potential stays constant at -25 mm Hg
Remains constant because of large molecules trapped within capillaries
Water potential is higher at artery than at vein
Water potential is higher outside the capillary bed than inside, so we get water flowing out from the capillaries into the interstitial fluid → FILTRATION at the artery
Water potential is higher inside the capillary bed at the vein, so reabsorption happens
