cells to organisms lecture mcq 2

negative feedback

to return a variable to a normal range (eg temperature regulation, blood glucose regulation)

Positive feedback

amplifies a stimulus and only contributes to homeostasis in animals in a small number of functions (childbirth, blood clotting, electrical impulses in nerves)

feedforward

anticipatory responses to expected change (eg increased heart rate in anticipation of exercise; increased secretion of insulin before food is digested to yield glucose; stimulation of gastric secretions due to thought/smell of food)

homeostasis

Maintaining a relatively constant internal environment (steady state) in the face of dynamic change

endocrine versus nervous signalling

interaction and cooperation examples between endocrine and nervous sytems

1. 1. Some nerves innervate endocrine glands eg.adrenal glands

2. 2. Hypothalamus and pituitary are brain regions that regulate endocrine function

3. 3. Blood pressure is regulated by nerves acting on the heart and blood vessels and by hormones acting on the kidneys to regulate blood volume

4. 4. Glial cells (including immune cells) in nervous system play an important role in nervous function

role of sensory receptors

transduce stimulus energy and transmit signals to the central nervous system: complex processing of sensory information to build percepts

order of sensory processing

describe how information is relayed and processed regarding PNS and CNS

what is cerebrospinal fluid

surrounds the brain and spinal cord and fills the ventricles. It is modified blood plasma

grey and white matter in the brain

fill in the blank

function of the spinal cord

Neuronal link between brain and PNS Integrating center for spinal reflexes

31 pairs of spinal nerves emerge from spinal cord through spaces formed between vertebrae

what happens at the synapse

neurotransmittersdiffuse short distances and bind to receptors on target cells

what are NTs supported by

glia

visceral afferent versus sensory afferent

Visceral afferent: Incoming pathway for information from internal viscera (organs in body cavities)

Sensory afferent: Somatic (body sense) sensation: arises from body surface and proprioception(touch, pain, orientation of body and limbs)

what are the two efferent components of the PNS and their functions

the motor system : carries signals to skeletal muscles and is mainly voluntary (though note reflexes and also eg diaphragm in breathing

the autonomic nervous system: regulates smooth and cardiac muscles and is generally involuntary

the enteric: exerts direct control over the digestive tract, pancreas, and gallbladder

the autonomic nervous system has→

sympathetic division regulates arousal and energy generation (“fight-or-flight” response)

parasympathetic division has antagonistic effects on target organs and promotes calming and a return to “rest-and-digest”functions

describe the autonomic nerve pathway

Extends from CNS to an innervated organ

Two-neuron chain Preganglionic fiber (synapses with cell body of second neuron) Postganglionic fiber (innervates effector organ)

what is a ganglion

a collection of cell bodies in the peripheral nervous system The equivalent in the CNS is a nucleus

what are visceral organs innervated by

Most (but not all) visceral organs are innervated by both sympathetic and parasympathetic fibers (eg sweat glands only receive sympathetic innervation)

In general produce opposite effects in a particular organ

Dual innervation of organs by both branches of ANS allows precise control over organ’s activity

what does an increase in action potential frequency cause

Increase frequency: more neurotransmitter released: bigger effect on target cell

function of motor neurons

Motor neurons are final common pathway by which various regions of CNS exert control over skeletal muscle activity– areas include spinal cord, motor regions of cortex, basal nuclei, cerebellum, and brain stem

Acetylcholinesterase

inactivates ACh, ends the end-plate potential and the action potential and resultant contraction

Ach at the neuromuscular junction(NMJ)

nicotinic ie respond to nicotine

When ACh receptors are activated, ion channels open allowing influx of current and depolarization of cell (end-plate potential)

chemical agents NMJ is susceptible too

Black widow spider venom causes explosive release of ACh: prolonged depolarization: respiratory failure

Botulinim toxin (C. Botulinim) blocks release of ACh: causes flaccid paralysis Food poisoning; Medical use; Cosmetic use.

Curare blocks action of ACh at receptor sites (antagonist, competitive with ACh). Used as an arrow poison by indigenous peoples of S. America

Organophosphates (eg Sarin) prevent inactivation of ACh– lung muscle paralysis – death by suffocation. Used as chemical weapons

two neurotransmitters involved in autonomic nervous signaling

epinephrine=adrenaline and norepinephrine=noradrenaline

differences in NT release between sympthatic and parasympathetic

Sympathetic: ACh secreted from pre ganglionic; NAd secreted from post ganglionic Also causes release of Ad from adrenal gland

Parasympathetic: ACh released from both pre ganglionic and post ganglionic neurons

types of cholinergenic receptors

bind ACh

Nicotinic receptors– found on postganglionic cell bodies of all autonomic ganglia

Muscarinic receptors– found on effector cell membranes

Andrenergic receptors

bind noradrenaline and adrenaline

receptor agonists versus antagonists

Receptor agonists: Bind to same receptor as neurotransmitter Elicit an effect that mimics that of neurotransmitter

Receptor antagonists: Bind to receptor Block neurotransmitter’s response

Regions of CNS Involved in Control of Autonomic Activities

prefrontal cortex through its involvement with emotional expression characteristic of individual’s personality

Hypothalamus plays important role in integrating autonomic, somatic, and endocrine responses that automatically accompany various emotional and behavioral states

Medulla within brain stem is region directly responsible for autonomic output

Some autonomic reflexes, such as urination, defecation, and erection, are integrated at spinal cord level

bronchodilator

Eg salbutamol (β2-adrenergic agonist) β2-adrenergic receptors are predominant receptors on bronchial smooth muscle

Physiology: Sympathetic nerves innervate bronchial smooth muscle When they release NAd (eg during exercise): bronchioles widen, making it easier to breathe Bronchodilator drugs act on these receptors to mimic the effect of endogenous neurotransmitter, widening bronchioles and making it easier to breathe

metoprolol

n anti-hypertensive: blocks β1 adrenergic receptors in heart muscle cells ‘β-blocker’ class of drugs

Physiology: sympathetic nerves speed up heart rate β-blockers block the effects of sympathetic nerves, decreasing heart rate and helping to lower blood pressure

describe the blood brain barrier

Tight junctions between endothelial cells lining cerebral blood vessels Specific arrangement of glial cells Prevents easy passage of large macromolecules and pathogens between the circulation and the brain

effects of serotonin being complex

what is muscle activity a response to

input from the nervous system '

Muscle cell contraction relies on the interaction between thin filaments, composed mainly of actin, and thick filaments, staggered arrays of myosin

what does the skeleton provide for muscles

a rigid structure to which muscles attach

what are muscle composed by

A skeletal muscle consists of a bundle of long fibres, each a single cell, running along the length of the muscle

Each muscle fiber is itself a bundle of smaller myofibrils arranged longitudinally

Skeletal muscle is also called striated (striped) muscle because the regular arrangement of myofilaments creates a pattern of light and dark bands

The functional unit of a muscle is called a sarcomere and is bordered by Z lines, where thin filaments attach

the sliding filament model

thin and thick filaments ratchet past each other longitudinally, powered by the myosin molecules – the muscle shortens

how does myosin facilitate muscle contraction

Each myosin has a long “tail” region and a globular “head” region

The head of a myosin molecule binds to an actin filament, forming a cross-bridge and pulling the thin filament toward the center of the sarcomere: the power stroke

Muscle contraction requires repeated cycles of this binding and release: “cross-bridge cycling”

why does muscle fatigue

Metabolic reasons: lack of substrate (ATP) or accumulation of metabolites that interfere with contraction Glycolysis and aerobic respiration generate the ATP needed to sustain muscle contraction During intense muscle activity, O2 becomes limiting & ATP is generated by lactic acid fermentation This activity generates less activity per glucose than glycolysis and can sustain contraction for only about 1 minute

function of tropomyosin

The regulatory protein tropomyosin and the troponin complex, a set of additional proteins, bind to actin strands on thin filaments when a muscle fibre is at rest This prevents actin and myosin from interactin

how do muscle fibers contract

The regulatory protein tropomyosin and the troponin complex, a set of additional proteins, bind to actin strands on thin filaments when a muscle fibre is at rest

This prevents actin and myosin from interacting

For a muscle fibre to contract, myosin-binding sites must be exposed

This occurs when calcium ions (Ca2+) bind to the troponin complex and expose the myosin-binding sites

Contraction occurs when the concentration of Ca2+ is high; muscle fibre contraction stops when the concentration of Ca2+ is low

why are motor nerves vital for skeletal muscle contraction

The stimulus leading to contraction of a muscle fibre is an action potential in a motor neuron that makes a synapse with the muscle fibre

The synaptic terminal of the motor neuron releases the neurotransmitter acetylcholine (ACh) ACh depolarizes the muscle (end plate potential), causing it to produce an action potential

Action potentials travel to the interior of the muscle fibre along transverse (T) tubules, causing the sarcoplasmic reticulum (SR) to release Ca2+

The Ca2+ binds to the troponin complex, initiating the muscle fibre contraction

When motor neuron input stops, the muscle cell relaxes - transport proteins in the SR pump Ca2+ out of the cytosol - regulatory proteins bound to thin filaments shift back to their starting positions

how are graded contractions produced

Contraction of a whole muscle is graded; the extent and strength of its contraction can be voluntarily altered 2 basic mechanisms by which the nervous system produces graded contractions

Varying the number of fibres that contract

Varying the rate at which fibres are stimulated

Each motor neuron may synapse with multiple muscle fibres, although each fibre is controlled by only one motor neuron

what does a motor unit consist of

a single motor neuron and all the muscle fibres it controls

tetanic muscle contraction

sustained muscle contraction, where a muscle doesn’t relax between contractions eg if you’re lifting a heavy weight.

skeletal muscle disorders

Amyotrophic lateral sclerosis/Motor Neurone Disease Unknown cause (genetics + environmental factors) Interferes with the excitation of skeletal muscle fibers; muscles atrophy and weaken. No cure or effective treatment

Multiple sclerosis Demyelinating disease with major immune component Unknown cause (genetics + environmental factors) Disorder of central nervous system

Myasthenia gravis An autoimmune disease that attacks ACh receptors on muscle fibres: muscle weakness (eye, limb, respiratory) 200-400 cases/million Treatments: cholinesterase inhibitors; immunosuppressants

Duchenne Muscular Dystrophy 1:5000 males at birth (X-linked) Genetic Lack of dystrophin (muscle protein) Muscles weaken and degenerate over time

what are cardiac gap junctions

electrical current spreads directly from one cell to another

what makes cardiac muscle unique

Cardiac muscle can generate action potentials without neural input (because of the pacemaker)

Cardiac muscle does NOT fatigue (lots of mitochondria)

No tetanic contraction

characteristics of smooth muscle

Smooth muscle is found mainly in walls of hollow organs such as those of the circulatory, digestive, and reproductive systems

Contractions are relatively slow and may be initiated by the muscles themselves

Contractions may also be caused by stimulation from neurons in the autonomic nervous system

Smooth muscle lacks striations because the actin and myosin are not regularly arrayed

Calcium ions enter the cytosol through the plasma membrane; smooth muscle contraction is regulated by Ca2+, but the mechanism is different

resistance versus endurance training on the heart

Endurance (aerobic) training: heart chambers increase in volume can pump more blood with each beat

Resistance training: heart chamber wall increases in mass: generates more force to pump against resistance

what happens to astronauts muscle in space

On earth we use anti-gravity muscles eg. calf (gastrocnemius, soleus), quadriceps, back, neck. Microgravity; little muscle contraction is needed; spacecraft physical work is undemanding. Without regular use and contraction of muscle, muscles weaken and deteriorate. Up to 20% loss of muscle mass on spaceflights lasting five to 11 days

Astronauts in the International Space Station (ISS) exercise for 2.5hrs/day to prevent muscle atrophy – even then it is not entirely successful and some atrophy still occurs

effect on astronauts heart

CVS function slows down in space Heart becomes more spherical in shape and loses muscle mass (use it or lose it)

Heart function is less efficient NASA study: 12 astronauts underwent ultra sound before, during and after spaceflight

Hearts become 9.4% more spherical Temporary change: shape reverted on return to earth

Consequences for blood circulation and fluid balance

what are the three classes of hormones and their descriptions

polypeptides, steroids, and amines

Polypeptides and most amines are water soluble

Steroid hormones and other largely nonpolar hormones are lipid soluble

Water-soluble hormones are secreted by exocytosis, travel freely in the bloodstream, and bind to cell-surface receptors

Lipid-soluble hormones diffuse across cell membranes, travel in the bloodstream bound to transport proteins, and diffuse through the membrane of target cells They bind to receptors in the cytoplasm or nucleus of the target cells

purpose of the hypothalamus

coordinates endocrine signaling It receives information from nerves throughout the body and initiates appropriate neuroendocrine signals

anterior versus posterior pituitary gland

At the base of the hypothalamus is the pituitary gland, composed of the posterior pituitary and anterior pituitary

The posterior pituitary stores and secretes hormones that are made in the hypothalamus Neural link (PP also known as neurohypophysis)

The anterior pituitary makes and releases hormones under regulation of the hypothalamus Vascular link (AP also known as adenohypophysis)

why does alchohol increase urine output

Alcohol inhibits secretion of ADH = increased volume of dilute urine

thyroid gland feedback loop

If thyroid hormone level drops in the blood, the hypothalamus secretes thyrotropin releasing hormone (TRH), causing the anterior pituitary to secrete thyroid-stimulating hormone (TSH) TSH stimulates release of thyroid hormone by the thyroid gland

goiter

Disruption of thyroid hormone production and regulation can result in serious disorders Thyroid hormone is the only iodine-containing molecule synthesized in the body Low levels of thyroid hormone, due to insufficient iodine, the pituitary continues to secrete TSH This causes the thyroid to enlarge, resulting in a goiter

function of the adrenal glands

The adrenal glands are located on top of the kidneys Each adrenal gland consists of two glands: adrenal medulla (inner) and adrenal cortex (outer)

Adrenal medulla secretes adrenaline and noradrenaline (fight, flight or freeze)

Adrenal cortex secretes corticosteroids – glucocorticoids and mineralocorticoids

Glucocorticoids eg cortisol, influence glucose metabolism and the immune system

Mineralocorticoids eg aldosterone, affect salt and water balance

type one versus type 2 diabetes

Type I diabetes Characterized by lack of insulin secretion (autoimmune destruction of b cells)

Type II diabetes Characterized by normal or even increased insulin secretion but reduced sensitivity of insulin’s target cells

describe the cardiac cycle

how to find cardiac output

Heart rate (beats/min) x stroke volume (mls/beat)

Standard at rest: 70bpm x 70ml/beat = 4900ml/min Approx. 5L/min

Exercise: increases several fold.

Untrained person maybe 20(female) - 25(male) L/min

Miguel Indurain (elite cyclist): peak CO of 50L/min

atrial fibrillation versus ventricular fibrilliation

Fibrillation Loss of coordination of electrical activity.

Can be corrected by defibrillation

Atrial fibrillation – weakness

Ventricular fibrillation - death within minutes Damage to heart muscle

boyles law

At constant temp, pressure and volume are inversely related

inhalation versus exhalation

how does transport of oxygen versus carbon dioxide differ

describe the Bohr shift

CO2 produced during cellular respiration lowers blood pH and decreases the affinity of hemoglobin for O2

describe Oedma

Build up of fluid in the interstitium , via Reduced [plasma proteins] Loss in urine (kidney disease) Reduced synthesis (liver disease) Dietary Increased capillary permeability Inflammation & allergic responses

Increased venous pressure

Uterine venous compression during pregnancy

Aeroplane flight (via decompression & immobility)

Lymph blockage Damage during surgery Parasitic infection