Human Anatomy and Physiology Week 7 Course Book PDF

SHAP001 Human Anatomy and Physiology Week 7 Course Book PRE-TUTORIAL A: AUTONOMOUS NERVOUS SYSTEM Autonomous Nervous System (Fill in the blanks) The ANS operates largely outside our awareness. It takes an...

SHAP001 Human Anatomy and Physiology Week 7 Course Book PRE-TUTORIAL A: AUTONOMOUS NERVOUS SYSTEM Autonomous Nervous System (Fill in the blanks) The ANS operates largely outside our awareness. It takes an important role in regulating the internal environment of the body. By increasing or decreasing its maintainhomoetasis activities, it helps _____________________________________in response to the changing physiological conditions due to the change of demands at a particular time. The ANS is a ________________system innervating the viscera (internal organs) which are under motifountary ________________ control. ANS consists of two antagonistic sub-systems: ________________ and sympathetic _____________________ nervous systems. parasympathetic Parasympathetic Division Sympathetic Division “Kicks in” during resting conditions, “Kicks in” only during exertion, stress, or for “Rest and Digest” emergency, for “Fight or Flight” Reduces metabolic rate and promotes Increases alertness, metabolic rate, and digestion muscular abilities SHAP001 Week 7 Coursebook 1  parasympathetic sympathetic TUTORIAL A: PARASYMPATHETIC AND SYMPATHETIC NERVOUS SYSTEM 1. Use the knowledge you know about sympathetic and parasympathetic nervous systems to explain the heartbeat rate regulation in the diagram below. brain parasympathetic faster SHAP001 Week 7 Coursebook 2  2. Put a tick (✔) to decide whether the activities in the first column belongs to sympathetic or parasympathetic nervous systems. Activities Sympathetic nervous systems Parasympathetic nervous systems Reading tightandflight rest anddigest Jumping Dancing Walking Studying Eating Swimming Sleeping Writing Speaking Reading Listening Drinking SHAP001 Week 7 Coursebook 3  TUTORIAL A: NERVE IMPULSE TRANSMISSION ALONG THE NEURONS Nerve impulses are electrical messages (also known as a______ p_________) that ction otential can travel at high speed along a neuron from the dendrite to the axon. actionpotential 1. Resting potential (resting membrane potential): When the axon is in the resting state (i.e. not transmitting nerve impulses),  a potential difference of approximately _____ mV 70 is maintained between the inside and outside of the axon.  The membrane is said to be polarized. Ionic basis of the resting potential: The unequal distribution of ions occurs for 2 major reasons: 1) The sodium/potassium PUMP ( ion channel) actively pumps Na+ ions and K+ ions into the axon. For every 3 Na+ ions pumped out, 2 K+ ions are pumped in. 2) The inside of the axon (the cytoplasm) already contains many –ve-charged proteins. 2. Action Potential negatively SHAP001 Week 7 Coursebook 4  Before we go to action potential, let’s take a look at the 3 different kinds of ION CHANNELS on the cell membrane. ALL these channels are CLOSED when resting. Open or closed in Open or closed in response to the presence of Open or closed in response to response to voltage neurotransmitters the physical stretching of the membrane I Conduction of nerve impulses  To initiate, the membrane is first required to depolarize, i.e. reverse the membrane potential. A PSFIntial  At the end, there will be a restoring phase that restores the membrane to be polarized, i.e. the resting state. This is known as repolarization. Ionic basis of the action potential: Depolarization:  When an impulse passes along the axon, mechanical-gated Na+ channels open and Na+ ions enter into the cell. Known as  55 (the threshold for eliciting the action If inside of the membrane reach –___mV all-or-none potential), then voltage-gated Na+ channels open and more Na+ ions (already 10 phenomeno times more concentrated outside) enter into the axon. n  Rapid Na+ entry depolarizes the cell, becoming +ve on the inside (___ mV) and 30 negative outside. This depolarization is known as the action potential. 785 78 SHAP001 Week 7 Coursebook 5  Repolarization and hyperpolarization:  At 0.5msec, the Na+ channels close and the voltage-gated K+ channels open causing more K+ ions to leave from the cell to the outside. This marks the beginning of the recovery process in which the inside of the axon regains its negative charge, i.e. re-polarization.  In fact K+ channels remain open and additional K+ leaves cell, hyperpolarizing it to –75mV.  Finally, voltage-gated K+ channels close, less K+ leaks out of the cell. The sodium/potassium PUMPS take over, and the cell returns to resting membrane potential. SHAP001 Week 7 Coursebook 6  TUTORIAL A: NERVE IMPULSES TRANSMISSION Fate of neurotransmitter: 1. Some will be degraded by the enzymes at the cleft. 2. Some will be recycled: neuron Post synaptic 1 Pre synaptic neurons s Retrograde L goingback What is the advantage of having synapse? To allow the u___________________ nidirectional transmission of nerve impulses. Because:  synaptic vesicles are found only on the pre-synaptic side of the cleft and  the protein receptors that linked to the Na+ ion channels are only on the post-synaptic side. Other types of synapses in our body: 1. SHAP001 Week 7 Coursebook 7  2. 3. Electrical synapses Found in neural systems that require the fastest possible response, such as defensive r____________ and some areas of brain and eye. esponse For examples, neurons allowing crayfish to escape from predators i.e. time between stimulus and lifesaving motor response. SHAP001 Week 7 Coursebook 8  TUTORIAL A: ALL-OR-NONE PHENOMENON What is all-or-none phenomenon? Let’s consider the following: y sub under If the strength of the stimulus is below the threshold (-55mV)  ____________ noactionpotential 30mV If the stimulus is above the threshold  a full-sized potential is evoked Further increase in the intensity of the stimulus  full sizedactionpotentialOccu ________________________ This is the all-or-none phenomenon which states the response of an excitable unit (axon) is independent of the intensity (size) of the stimulus. Then, it comes to a question – how do we differentiate a light touch from a firmer touch? 1. F_________ of impulses requency  firm pressure generates impulses at a higher frequency 2. N_________ of sensory neurons activated umber  firm pressure stimulates more neurons than does a light touch SHAP001 Week 7 Coursebook 9  TUTORIAL A: IMPORTANCE OF THE REFRACTORY (INEXCITABILITY) PERIOD Resting Nationsentercen 2k 1 99,5 9IE ActionPotential 2ktions Repolarisationpolarisation negative Nationsgoingout entercell3,3 i.e. the threshold becomes higher than –____mv or above 60 Importance of the refractory period: 1. To ensure action potential can only be propagated in a forward direction, i.e. to those regions that are not refractory. This prevents spreading out the action potential in both directions. Directionof action potential movement possibilitytobe excited 2. By the end of the refractory period the action potential has passed further down the nerve. The second action potential will thus be separated from the first one by the refractory period. SHAP001 Week 7 Coursebook 10  TUTORIAL A: TRANSMISSION SPEED thickness The transmission speed depends upon the 1. Axon diameter, and 2. The presence of myelin sheath. 1. Axon diameter The thicker the axon, the ___________ is the rate of nerve impulse transmission. higher It is because a large axon offers less resistance to local current flow, and it provides greater surface area of membrane over which ionic exchange takes place. 2. Myelin Sheath Run Jump walk n n SHAP001 Week 7 Coursebook 11