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102BMS Anatomy = study of internal and external body structures and their physical relationships among other body parts as revealed by dissection Subdivided into: 1. Gross anatomy: involves examining large structures e. major organs. There are many different forms of gross anatomy:  Surface anatomy...

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102BMS

Anatomy = study of internal and external body structures and their physical relationships among other body parts as revealed by dissection Subdivided into: 1. Gross anatomy: involves examining large structures e.g. major organs. There are many different forms of gross anatomy:  Surface anatomy: study of general form and superficial markings  Regional anatomy: focuses on the anatomical organisation of specific areas of the body  Systemic anatomy: study of the structure of organ systems  Clinical anatomy: includes number of subspecialties important in clinical practice  Developmental anatomy: describes the changes in form that take place between conception and adulthood. Considers anatomical structures over a broad range of sizes – from single cell to adult human. o Embryology – changes from egg o foetus at 8th week (in utero) 2. Microscopic anatomy: deals with structure that we cannot see without magnification  Cytology: study of internal structure of individual cells  Histology: examination of tissues 3. Pathology: study of disease Physiology = study of how living organisms perform their functions. Subdivided into: 1. Cell physiology: study of the function of the cells. It also looks at events involving the atoms and molecules important to life. It includes both chemical process within cells and chemical interactions among cells 2. Systemic physiology: includes all aspects of the functioning of the specific organs systems 3. Pathological physiology: study of the effects of diseases on organ functions or system functions Atoms = smallest stable units of matter. They combine to form molecules with complex shapes Cells = smallest living units in the body. Complex molecules can form various types of large structures called organelles

Tissue = group of similar or same cells working together to perform one or more specific function Organs = two or more tissues working together to perform the specific function Organ system = group of organs interacting with each other to perform a particular function Organism = is the highest level of organism

Anatomical position = reference point for all anatomical nomenclature o Upright posture o Head, eyes, toes forward o Arms by side o Palms facing backwards

Term Superior (cephalad) Inferior (caudad)

Definition Towards the head Away from the head

he back of the body he front of the body m the midline of the body he midline of the body m the surface of the body he surface of the body ar the centre of the body or to or away from the centre ody or organ n extremity that is closer to t of attachment to the trunk n extremity that is further to t of attachment to the trunk ng to the outer boundary of y cavities e.g. oesophagus ng to the internal organs Homeostasis = refers to the existence of stable internal environment Homeostatic regulation is the adjustment of physiological system to preserve homeostasis. It involves two mechanisms: 1. Autoregulation: process that occurs when a cell, tissue, organ or organ system adjusts in response to some environmental change 2. Extrinsic regulation: process that results from activities of the nervous system or endocrine system. These organ systems detect an

environmental change and send an electrical signal or chemical messenger to control or adjust the activities of another or many other systems simultaneously Receptor = sensor that is sensitive to a particular stimulus or environmental change Control centre = receives and processes the information supplied by the receptor and sends out commands to effectors Effectors = cell or organ that responds to the commands of the control centre and whose activity either opposes or enhances the stimulus Feedback mechanisms: 1. Negative feedback: most common form of control; homeostatic mechanism that opposes or resists a change in the body’s internal conditions. It prevents homeostatic responses from over compensating. It provides long-term control over the body’s internal conditions and systems. They maintain a normal range rather than a fixed value 2. Positive feedback: initial stimulus produces a response that exaggerates or enhances the original change in conditions. This kind of escalating cycle is often positive feedback loop. They are typically found when a potentially dangerous or stressful process must be completely quickly to restore homeostasis. Blood glucose negative feedback: Glucose is the transport carbohydrate in animals, and its concentration in the blood affects every cell in the body. Its concentration is therefore strictly controlled within the range 80-100 mg 100cm-3, and very low level (hypoglycaemia) or very high levels (hyperglycaemia) are both serious and can lead to death. Blood glucose concentration is controlled by the pancreas. The pancreas has glucose receptor cells, which monitor the concentration of glucose in the blood, and it also has endocrine cells (called the islets of Langerhans), which secrete hormones. The α cells secrete the hormone glucagon, while the β cells secrete the hormone insulin. These two hormones are antagonistic, and have opposite effects on blood glucose: • insulin stimulates the uptake of glucose by cells for respiration, and in the

liver it stimulates the conversion of glucose to glycogen (glycogenesis). It therefore decreases blood glucose. • glucagon stimulates the breakdown of glycogen to glucose in the liver (glycogenolysis), and in extreme cases it can also stimulate the synthesis of glucose from pyruvate. It therefore increases blood glucose. After a meal, glucose is absorbed from the gut into the hepatic portal vein, increasing the blood glucose concentration. This is detected by the pancreas, which secretes insulin from its β cells in response. Insulin causes glucose to be taken up by the liver and converted to glycogen. This reduces blood glucose, which causes the pancreas to stop secreting insulin. If the glucose level falls too far, the pancreas detects this and releases glucagon from its a cells. Glucagon causes the liver to break down some of its glycogen store to glucose, which diffuses into the blood. This increases blood glucose, which causes the pancreas to stop producing glucagon. Thermoregulation In humans temperature homeostasis is controlled by the thermoregulatory center in the hypothalamus. It receives input from two sets of thermoreceptors: receptors in the hypothalamus itself monitor the temperature of the blood as it passes through the brain (the core temperature), and receptors in the skin monitor the external temperature. Both pieces of information are needed so that the body can make appropriate adjustments. The thermoregulatory center sends impulses to several different effectors to adjust body temperature

Effector

Response to low temperature

Smooth muscles in peripheral arterioles in the skin.

Muscles contract causing vasoconstriction. Less heat is carried from the core to the surface of the body, maintaining core temperature. Extremities can turn blue and feel cold and can even be damaged (frostbite).

Muscles relax causing vasodilati More heat is carried from the co the surface, where it is lost by convection and radiation. Skin t red.

Sweat glands

No sweat produced.

Glands secrete sweat onto surfa skin, where it evaporates. This is endothermic process and water high latent heat of evaporation, takes heat from the body.

Erector pili muscles in skin (attached to skin hairs)

Muscles contract, raising skin hairs and trapping an insulating layer of still, warm air next to the skin. Not very effective in humans, just causing “goosebumps”.

Muscles relax, lowering the skin and allowing air to circulate ove skin, encouraging convection an evaporation.

Skeletal muscles

Muscles contract and relax repeatedly, No shivering. generating heat by friction and from metabolic reactions.

Adrenal and

Glands stop releasing adrenalin Glands secrete adrenaline and ncrease thyroxine. tissues, ng helter,

Response to high temperat

Stretching out, finding shade, swimming, removing clothes.

Hypothermia could lead to coma and stop breathing

Heat stroke causes multiple organ failure, brain damage and death

Parturition (child birth) Nervous system sends signals via electrical signals. Endocrine system sends signals via chemical signals. These chemicals are called hormones. Hormones are chemical messengers that are released in one tissue and transported in the bloodstream to alter the activities of specific cells in other tissues. There are different types of hormones: o steroid hormones: includes the sex hormones all of which are lipids made from cholesterol. They are released by the reproductive organs, by the cortex of the adrenal glands and by the kidneys. o amino acid derivatives: small molecules that are structurally related to amino acids, especially tyrosine e.g. adrenaline

o peptide hormones: chain of amino acids. Most peptide hormones are synthesized are prohormones – inactive molecules that are converted to active hormones before or after fI they are secreted. E.g. insulin

There are four types of intercellular signalling: 1. Endocrine: most common type of cell signaling and involves sending a signal throughout the whole body by secreting hormones into the bloodstream of animals or the sap in plants. The cells that produce hormones in animals are called endocrine cells. For example, the pancreas is an endocrine gland and produces the hormone insulin, which regulates the uptake of glucose in cells all over the body. Examples of hormones that function in an endocrine manner include testosterone, progesterone and gonadotropins. 2. Paracrine: signaling and target cells are nearby. signalling molecules are released from paracrine cells and diffuse locally through the extracellular fluid, targeting cells that are nearby, thus acting as local mediators. Many of the cells that are involved in inflammation during infection, or that regulate cell proliferation utilise this type of signalling. For example, cancer cells sometimes enhance their own survival or proliferation in this way. Examples of signalling molecules that often function in a paracrine manner include transforming growth factor-β (TGF-β) and fibroblast growth factors (FGFs). 3. Autocrine: Some signal molecules travel very locally, that is, the secreting cell and target cell are the same. An example is the proliferation of T cells of the immune system which is induced by antigens released by T cells. 4. Synaptic: Neurons communicate at structures called synapses in a process called synaptic transmission. The synapse consists of the two neurons, one of which is sending information to the other. The sending neuron is known as the pre-synaptic neuron (i.e. before the synapse) while the receiving neuron is known as the post-synaptic neuron (i.e. after the synapse). Although the flow of information around the brain is

achieved by electrical activity, communication between neurons is a chemical process. When an action potential reaches a synapse, pores in the cell membrane are opened allowing an influx of calcium ions (positively charged calcium atoms) into the pre-synaptic terminal. This causes a small 'packet' of a chemical neurotransmitter to be released into a small gap between the two cells, known as the synaptic cleft. The neurotransmitter diffuses across the synaptic cleft and interacts with specialized proteins called receptors that are embedded in the postsynaptic membrane. These receptors are ion channels that allow certain types of ions (charged atoms) to pass through a pore within their

structure. The pore is opened following interaction with the neurotransmitter allowing an influx of ions into the post-synaptic terminal, which is propagated along the dendrite towards the soma.

Nervous system is an electrochemical communication system. It consists of the brain, spinal cord, peripheral nerves and sense organs. Their functions include:  Directs immediate responses to stimuli  Provides the basis for conscious experience  Provides and interprets sensory information about external conditions o Receives sensory messages from the external environment  Process and interpret sensory input and decide if action is needed  Coordinates or moderates activities of other organ systems o Sends out messages to muscles and glands – producing organised movements and secretions Receptor – has a characteristic sensitivity. This feature is called receptor specificity. This can result from the structure of the receptor cell, or from the presence of accessory cells or structures that shield the receptor cell from other stimuli. Receptor Type Stimuli Baroreceptor – free nerve endings Detect pressure changes in the walls that branch within the elastic tissues of blood vessels and in portions of in the wall the digestive, respiratory and urinary tracts Osmoreceptor Changes in solute concentration Nociceptor – are free nerve endings Respond to tissue damage. May also with large receptive fields be sensitive to extreme temperature, mechanical damage and dissolved chemicals, e.g. chemicals released by injured cells. Mechanoreceptor – sensitive to Respond to mechanical forces stimuli that distort their plasma membrane Photoreceptor Respond to light Proprioceptor – three major groups Monitor the position of joints, the are muscle spindle, golgi tendon tension in tendons and ligaments, organ and receptors in joint capsule. and the state of muscular contraction Thermoreceptor – free nerve endings Respond to temperature changes located in the dermis, in skeletal muscles, in the liver and in the hypothalamus. Phasic receptor – active when the temperature is changing but they quickly adapt to a stable temperature. Gustatory receptors Respond to chemicals in food

Central Nervous System(CNS):  Brain  Spinal cord

Peripheral Nervous system (PNS):  Nerves outside the brain and spinal cord  Afferent division – Nerve fibers that carry information to the CNS from receptors in peripheral tissues and organs. Receptors are sensory structures that either detect changes in the environment or respond to specific stimuli  Efferent division - Nerve fibers that carry impulses away from the CNS to muscles, glands and adipose tissues. These are called effectors o Somatic system: controls skeletal muscle contractions; voluntarily. Single motor neuron travels directly to the skeletal muscle without the mediation of ganglia – bund of nerves fibers holding cell bodies; located in ANS. Consists of:  Peripheral nerve fibers that send sensory information to the CNS  Motor fibers that project to skeletal muscle  Reflex arc – neural circuit automatic link between a sensory input and specific motor output  Ach – excitatory only  Sensory neurons – ranges in size  Motor neurons – all large neurons are myelinated o Autonomic Nervous system – coordinates cardiovascular, respiratory, digestive, urinary and reproductive functions. It adjust international conditions at the subconscious level. Functions:  to maintain homeostasis by involuntary, reflexive manner.  Exerts influence by rapid transmission of electrical impulses via nerve fibers  ANS and endocrine system coordinate the regulation and integration of the body function  Coordinates cardiovascular, respiratory, digestive, urinary and reproductive functions by adjusting internal bodily fluid constituents  Visceral effector does not depend on the ANS to function – only need to adjust to body’s changing needs.

Includes:  Sympathetic division: adrenergic synapses; short preganglionic fibers; long postganglionic fibers; prepares body for fight-or-flight response  Parasympathetic division: cholinergic synapse; long preganglionic fibers; short postganglionic fibers; rest and repose. Acts to oppose the actions of sympathetic nervous system. Doesn’t discharge as a complete system. In non-emergencies, allows us to rest and digest. Generally dominant – saves energy. Essential for life. Ganglionic neurons have nicotine receptors, which are excitated by Ach. Muscarinic receptors at neuromuscular or neuroglandular junctions produce either excitation or inhibition, depending on the action of enzymes triggered by G protein activation when ACh binds to the receptor. Effects are generally bried and restricted to specific organs and sites Most organs are innervated by both parasympathetic and sympathetic division at the same time - dual innervation. E.g. heart but vagal innervation controls the heart rate  Parasympathetic (Vagal – controlled by vagus nerve) innervation – decreases contraction  Sympathetic innervation – increases contraction Fight-or-flight response:  Stimulation of preganglionic neurons – release Ach at synapses with ganglionic neurons = excitatory.; release neurotransmitters at specific target organs  Most ganglionic neurons release noradrenaline – adrenergic receptor. Some do release Ach. Effects of Noradrenaline at postsynaptic membrane persist for few seconds.

Rest and Repose:  All parasympathetic postganglionic fibers release Ach, synthesized from acetyl CoA and choline, – cholinergic receptor  Effects of Ach are short-lived as most are inactivated by acetylcholinesterase. The effects are localized and last few seconds at most Sensory neurons:  Form afferent division of the PNS  Deliver information from sensory receptor to the CNS  Cell bodies of sensory neurons are located in peripheral sensory ganglia (ganglion is collection of neuron cell bodies in the PNS)  Unipolar neurons whose processes, known as afferent fibers, extend between a sensory receptor and the CNS.  Somatic sensory neurons maintain the outside world and our position within  Visceral sensory neurons monitor internal conditions and the status of other organ systems Motor neurons:  Form efferent division of the PNS  Neurons carry instructions from the CNS to peripheral effectors in a peripheral tissue, organ or organ system  Axons travelling away from the CNS are called efferent fibers.  Somatic motor neurons that innervate skeletal muscles. Cell body of a somatic motor neurons lies in the CNS and its axon extends into the periphery within a peripheral nerve to innervate skeletal muscle fibers at neuromuscular junction  Visceral motor neurons innervate all peripheral effectors other than skeletal muscles – that is smooth muscle, cardiac muscle, glands and adipose tissue. The axons of visceral motor neurons in peripheral autonomic ganglia. The neurons whose cell bodies are located in those ganglia innervate and control peripheral effectors. The axons extending form the CNS to an autonomic ganglion are called preganglionic fibers, and axons connecting the ganglion cells with the peripheral effectors are known as postganglionic fibers. Interneurons:  Located between sensory and motor neurons

 Most located in brain and spinal cord, but some are in autonomic ganglia  Distribute sensory information and coordinate motor activity  More complex the response to a given stimulus, the more interneurons are involved  Play a part in all higher function such as memory, planning and learning

Dendrites:  help increase the SA of the cell body and are covered with synapses  receive information from other neurons and transmit electrical stimulation to the cell body  extend out from the cell body Cell body:  where signals from the dendrites are integrated and passed on  cell body and nucleus do not play an active role in the transmission of the neutral signal  the cytoskeleton of the perikaryon (cytoplasm surrounding the nucleus) contains neurofilaments and neurotubules. Bundles of neurofilaments, called neurofibrils, extend into the dendrites and axon, providing internal support for them  contains organelles, numerous mitochondria, free and fixed ribosomes and membrane of RER, that provide energy and synthesize organic materials giving the perikaryon a grainy appearance  lack centrioles

Myelinated neurons:  speeds up the rate of ele...