Unit 2: Physiology Flashcards
Includes Unit 2 topics: The nervous system, Hormones and homeostasis, The circulatory system, Digestion and excretion (35 cards)
Outline the roles of sensory receptors in mammals in converting different forms of energy into nerve impulses
Sensory receptors are the specialised part of sensory neurones that allow external stimuli to be detected.
The types of sensory receptors (and their stimuli) include: Mechanoreceptors(physical force), Thermoreceptors(temperature), Chemoreceptors(dissolved chemicals), nociceptors(pain), proprioceptors(positional information)
Describe, with the aid of diagrams, the structure and functions of sensory and motor neurones
Motor neurons: motor neurones in animals are part of the central nervous system and they connect to muscles, glands and organs throughout the body. Transmit impulses from spinal cord to skeletal muscles to control movement. Lower motor neurones: travel from spinal cord to muscle. Upper motor neurones: travel between the brain and spinal cord. Are multipolar(one axon and several dendrites).
Sensory Neurons: activated by sensory input from the environment. Most sensory neurons are pseudo-unipolar, which means they have only one axon split into two branches
Describe and explain how the resting potential is established and maintained
Potassium concentration is higher in the cell, while sodium is higher outside the cell. This gradient is maintained by a sodium-potassium pump(which uses ATP to maintain this gradient). These concentration gradients are a form of chemical energy.
Describe and explain how an action potential is generated
If sodium ions influx, more sodium channels open as they are voltage gated. This temporarily changes the membrane potential significantly. Once initiated an AP has a magnitude independent of the strength of the stimulus. AP are an all or none response. If a large enough stimulus is present an action potential is generated. AP has constant magnitude and regenerates the same potential in adjacent areas of the membrane. AP can therefore spread along axons/dendrites for long distance communication
Describe and explain how an action potential is transmitted in a myelinated neuron, with reference to the roles of voltage-gated sodium ion and potassium ion channels
The sodium inflow in the rising AP phase creates a current that depolarises the adjacent region. This process is repeated until the end of the axon/dendrite. Magnitude will be the same at every location. The zone immediately behind the AP is in the refractor period so APs can’t go backward
Outline the significance of the frequency of impulse transmission
AP has a constant magnitude but a neuron can produce hundreds of APs a second. The information about the environment is encoded in frequency not amplitude. Strong stimulus= more frequent AP. Small stimulus=less frequent AP
Outline the role of neurotransmitters in the transmission of action potentials
A neurotransmitter molecule can bind to different types of receptors that can excite or inhibit the postsynaptic cell. Neurotransmitter signalling is terminated by several methods: simple diffusion away from the membrane, recapture by the presynaptic neurone(allows recycling), enzymatic hydrolysis
Outline the role of synapses in the nervous system
Neurotransmitters often bind to ligand-gated ion channels. This opens channels that allow specific ions across the postsynaptic membrane. Two outcomes from this process: Excitatory postsynaptic potential(K+ and Na+ acts to bring membrane potential to threshold), and Inhibitory postsynaptic potential(Cl- act to do the opposite).
Show understanding of the difference in structural features of the brain in various animals
Chordata and Echinodermata: Brain and largely dorsally localised nerve cord
Arthropoda, Nematoda, Annelida, Mollusca: brain and largely ventrally localised nerve cord
Platyhelminthes: Nerve ring and nerve cord
Cnidaria: Diffuse nerve net
Porifera: no nerve cells
Demonstrate understanding of the role of the central nervous system in disease
Alzheimer’s: neurodegenerative disease, causing loss of neurons in the brain. Starts in the hippocampus and spreads in a predictable pattern to other regions of the brain. 70% of cases of dementia. Affects first memory and ability to perform task and movements, followed by decline of behavioural, social and verbal skills.
Parkinson’s: neurodegenerative disease, caused by neuronal loss in an area of the midbrain, the substantia nigra. Causes movement disorder and is characterised by tremors and muscular rigidity. Proteins aggregate into Lewy bodies in neurons. Eventually leads to dopamine reduction.
Compare and contrast the structure and function of myelinated and non-myelinated neurons
Lipid-rich substance surrounding the axons to insulate them. Casing made of oligodendrocytes and Schwann cells extensions. Myelin wraps the nerve in segments, with gaps called Nodes of Ranvier. Myelin increases the speed at which electrical impulses travel along the axon by forcing them to ‘jump’ from one node of Ranvier to another. ‘Fuelling station’ for the axon after the generation of electrical impulses. Coordinates the transport of cytoskeletal proteins and organelles. Demyelination is the hallmark of multiple sclerosis and other neuro-degenerative diseases. Similar structure found in some invertebrates(shrimps, annelid worms).
Interpret graphs of the voltage changes taking place during the generation and transmission of an action potential
Resting potential: -70 mV membrane potential
Threshold: -45mV membrane potential
Strong depolarizing stimulus: 0-3 seconds increases from resting to threshold.
Action potential: +35 mV membrane potential. 3-4 seconds increases from threshold to action potential.
4-6 seconds: decrease back down to resting potential
Understand the term ‘endocrinology’ and why animals and humans need an endocrine system
Endocrine system: Hormones are chemical signalling molecules that travel through the blood and reach every part of the body but only target cells have receptors that allow them to respond.
Why: Required for effective cell-cell communication in large, complex multicellular organisms. Monitor and coordinate internal environment and make appropriate adaptive changes. Regulate growth, development, reproduction, senescence. Enable you to respond and adapt to changes in external environment.
Define the term hormone and explain the different types
A chemical messenger produced and secreted by a specialized endocrine gland that is transported in the bloodstream to a distant target organ/cell where it elicits a physiological response.
Proteins: Growth hormone(hydrophilic)
Cholesterol Derivates: Steroids and Vitamin D(Hydrophobic)
Modified Amino Acids: Adrenaline(hydrophilic) and Thyroid hormones(hydrophobic)
Understand the concepts of hormone regulation and hormone action
Hormone action: Affect growth, development, metabolic activity and function of tissues. May be stimulatory or inhibitory. May act on several tissues or just one specific target tissue- major difference between endocrine and nervous system. Responsive tissues must have specific receptors for that hormone.
home regulation: By physiological changes(blood glucose regulates insulin and glucagon release from pancreas), by endogenous rhythms(ultradian-cycles in minutes: GnRH pulses(90-120 min.)), by feedback mechanisms(mostly negative(maintains homeostasis) but some positive(much less common))
Be able to give an explanation of the pituitary gland and give an example of a system that the pituitary regulates
Pituitary Gland: ‘Conductor of he Endocrine Orchestra’. Organizes appropriate hormonal responses to stimuli from higher centres of brain in response to external or internal environmental changes.
Systems: Growth, Metabolism, Stress response, reproduction, lactation, water and salt balance, birth, and feeding behaviour.
Be able to give a basic explanation of the regulation of glucose levels in man
Insulin: Go(glucose uptake in muscle and adipose tissue, glycolysis, glycogen synthesis, protein synthesis, and uptake of ions). Stop(proteolysis, ketogenesis, lipolysis, glycogenolysis, gluconeogenesis).
Insulin and glucagon act reciprocally. Insulin=fed state. Glucagon=fasted state
Explain the need for transport systems in multicellular animals
Link exchange surfaces with cells throughout the body. Small molecules move between cells and their surroundings by diffusion. Diffusion is only efficient over small distances because the time it takes to diffuse is proportional to the square of the distance. The circulatory system connects the fluid that surrounds cells with the organs that exchange gases, absorb nutrients, and dispose of waste.
Describe the different types of circulatory systems
Open: Hemolymph in sinuses surrounding organs. Open veins.
Closed: Interstitial fluid. Small branch vessels in each organ.
Single: one way all around. Ventricle, Artery, Gill capillaries, Systemic capillaries, vein, atrium.
Double: Two way. Right ventricle, lung capillaries, Left atrium, Left ventricle, systemic capillaries, right atrium.
Explain the structure and functions of arteries, arterioles, capillaries, venules and veins
Artery: Endothelium, smooth muscle, connective tissue, arteriole
Capillary: Endothelium, Basal Lamina. Are only slightly wider than a red blood cell. Have thin walls to facilitate the exchange of materials. Capillaries in major organs are usually filled to capacity. Exchange between the blood and interstitial fluid takes place across the thin endothelial walls of the capillaries. The difference between blood pressure and osmotic pressure drives fluids out of capillaries at the arteriole end and into capillaries at the venule end. Most blood proteins and all blood cells are too large to pass through the endothelium.
Vein: Venule, Connective tissue, Smooth muscle, Endothelium
Relate the external and internal structure of the mammalian heart to its function
Atrioventricular valves: separate each atrium and ventricle
Semilunar valves: control blood flow to the aorta and the pulmonary artery.
1. Atrial and ventricular diastole(relax). Both relaxed blood flows into the atria and ventricles.
2.Atrial systole(contracts) and ventricular diastole(relax). Atria contracts blood flows into the relaxed ventricles.
3. Ventricular systole(contracts) and atrial diastole(relax). Ventricle contracts blood exits, atria relaxed blood enters.
Describe the cardiac cycle
Blood begins its flow with the right ventricle pumping blood to the lungs via the pulmonary arteries. In the lungs, the blood loads O2 and unloads CO2. Oxygen-rich blood from the lungs enters the heart at the left atrium via the pulmonary veins. It is pumped through the aorta to the body tissues by the left ventricle. The aorta provides blood to the heart through the coronary arteries. Blood returns to the heart through the superior vena cava(head, neck, and forelimbs) and inferior vena cava(trunk and hind limbs). The superior and inferior vena cava flow into the right atrium.
Describe how heart action is initiated and coordinated
With each heartbeat, an electrical signal travels from the top of the heart to the bottom, causing the heart to contract and pump blood. the cardiac electrical system causes the heart to contract in a coordinated manner, maximizing the efficiency of the beating heart.
Describe structure of the blood
Blood in vertebrates is a connective tissue consisting of several kinds of cells suspended in a liquid matrix called plasma. The cellular elements occupy about 45% of the volume of blood.
Red blood cells: (erythrocytes) transport O2.
White blood cells: (leukocytes) function in defence
Platelets: fragments of cells that are involved in clotting
