Phase 1 - Week 7 (Autonomic Nervous System, Autonomic Dysreflexia), Phase 3 - Week 1 (Heart, Murmurs) Flashcards
List the functions of the autonomic nervous system
- Digestion
- Defecation
- Cardiorespiratory
- Stress response
- Genitourinary
- Sexual
- Exercise ability
- Maintain electrolytes
Is the autonomic nervous system under voluntary or involuntary control?
Generally subconscious, element of conscious control - can be overridden consciously (e.g. breathing rhythm)
Describe the divisions of the autonomic nervous system
- Sympathetic nervous system
- Parasympathetic nervous system
Sympathetic nervous system
- Accelerator
- Fight and/or flight (stress response)
- Origin - thoracolumbar origin
- Ganglia = next to spinal cord
What are the neurotransmitters of the sympathetic nervous system?
Acetyl choline at pre-ganglionic synapse Noradrenaline at post-ganglionic synapse
List the effects brought about by the sympathetic nervous system
- Vasoconstriction of vessels in the skin and gut
- Bronchodilation
- Increased heart rate and myocardial contractility
- Increased blood pressure
- Pupil dilation
- Inhibition of the bladder
- Vasodilation of vessels to skeletal muscles
Give the exceptions to the origin and neurotransmitters of the sympathetic nervous system
Origin = cervical ganglia (head + arms) Neurotransmitters = post ganglionic acetyl choline at sweat glands + deep muscles
List the types of post-ganglionic receptors of the sympathetic nervous system
Alpha receptors: - Alpha 1 = arteriole constriction - Alpha 2 = coronary + venous vasoconstriction Beta receptors: - Beta 1 = heart, some in brain - Beta 2 = everything else - smooth muscle relaxation, uterus, gut, bladder, lungs, eye
Parasympathetic nervous system
- Brake - Rest/digest - Origin = craniosacral outflow - Ganglia = diffusion near site of action
What are the neurotransmitters of the parasympathetic nervous system?
Acetyl choline pre and post-ganglion
List the effects of the parasympathetic nervous system
- Constrict pupils 2. Mucous membranes engorge 3. Increase salivation 4. Increase gastric secretions 5. Increase intestinal blood flow 6. Decrease heart rate/blood pressure
List the origins of the parasympathetic nervous system
Cranial - - 3 = pupillary constriction - 7 = mucous membranes - 9 = salivation - 10 = vagus nerve Sacral - - 2 - 3 - 4
Describe the receptors of the parasympathetic nervous system
Muscarinic receptors: - M1,4,5 = brain - M2 = heart - M3 = salivary glands, gut, bladder, blood vessels Nicotinic receptors: - N1, N2 - motor end plate (near skeletal muscle)
List the functions of the brain stem
- Cranial nerve function - Respiration, cardiovascular, sleep, arousal, consciousness - Conduit function - spinothalamic, corticospinal
List the cranial nerves and their functions
- Olfactory nerve - smell 2. Optic nerve - visual 3. Oculomotor nerve - eye movement 4. Trochlear nerve - eye movement 5. Trigeminal nerve - face sensation + muscles of mastication 6. Abducens nerve - eye movement 7. Facial nerve 8. Vestibulocochlear nerve - hearing and balance 9. Glossopharyngeal nerve - oral sensation, taste and salivation 10. Vagus nerve - parasympathetic 11. Accessory nerve - shoulder elevation, head turning 12. Hypoglossal nerve - tongue movement
Describe the parasympathetic sensory pathway
- Sensory interoceptors 2. CNS 3. Preganglionic motor neurone
Describe the parasympathetic motor pathway
- Preganglionic motor cell body 2. Preganglionic motor neuron 3. Automatic ganglion 4. Postganglionic neuron 5. Effector
Describe the sympathetic pathway
- Preganglionic motor cell body 2. Preganglionic motor fibres 3. Autonomic ganglion 4. Postganglionic motor fibres
What is the chemical formula for adrenaline
C9H13NO3
Where is adrenaline produced?
Adrenaline and noradrenaline are produced in the medulla of the adrenal glands and in some neurones of the CNS
What triggers the production of adrenaline?
The sympathetic nervous system
Describe tissue specificity of adrenaline
Different action depending on tissue it is acting on due to different receptors e.g. smooth muscle relaxation in airways, smooth muscle contraction in arterioles
What is the overall effect of adrenaline
- Response to acute stress, ‘fight or flight’ - Stimulatory effect on alpha and beta adrenic receptors (adrenoreceptors) of sympathetic nervous system - agonist
List the actions of adrenaline
- Increase HR 2. Increased BP 3. Expanding bronchi 4. Pupil dilation 5. Increased blood flow to skeletal muscle 6. Alters metabolism - maximise blood glucose levels esp. in brain, + fatty acids
Describe the production of adrenaline
Tyrosine -> noradrenaline -> adrenaline (methylation, + of methyl group)
How is the action of adrenaline halted?
Metabolic breakdown, re-uptake into nerve endings or diffusion from action sites
Define heart rate
Number of heartbeats per unit time, usually beats per minute
What is the normal resting heart rate?
70-90 BPM
How is heart rate controlled?
Sympathetic control: - Release of adrenaline and noradrenaline increases HR Parasympathetic control: - Release of acetyl choline decreases HR
What is responsible for controlling heart rate?
Cardiorespiratory centre in the medulla oblongata
Define blood pressure
Pressure exerted by the blood on the walls of blood vessels
Define systolic and diastolic pressure
Systolic = max arterial pressure during ventricular systole Diastolic = min arterial pressure during dilation of ventricles
What is normal blood pressures?
120/80 -> 140/90
How is blood pressure regulated?
- Baroreceptors - medulla, ANS changes pressure by changing force/speed of contractions + systemic vascular resistance - Baroreceptors regulate secretion of ADH, changing blood volume therefore pressure - Aldosterone (steroid hormone) stimulates sodium retention/potassium secretion by kidneys to change the blood volume - Renin secretion by the kidneys
Define autonomic dysreflexia
A condition occurring primarily in patients with spinal cord injury above T6 in which an external or bodily stimuli causes an imbalanced reflex sympathetic discharge, leading to potentially life-threatening hypertension.
What is the effect of untreated autonomic dysreflexia?
- Seizures - Retinal haemorrhage - Pulmonary oedema - Renal insufficiency - MI - Cerebral haemorrhage - Death
Describe the development of autonomic dysreflexia
- Strong sensory input - intact peripheral nerves -> spinal cord (common origins = bladder, bowel) 2. Reflex sympathetic surge from thoracolumnar sympathetic nerves 3. Widespread vasoconstriction - hypertension 4. Brain attempts to resolve - inhibitory impulses to sympathetic surge, decrease HR to decrease BP through vagus nerve - spinal cord damage doesn’t allow
Describe the measures taken to prevent autonomic dysreflexia
- Bladder and bowel care (catheterisation etc.) - Education - recognise early symptoms - Home blood pressure monitoring
List the symptoms of autonomic dysreflexia
- Anxiety and apprehension - Palpitations - Hypertension - Pounding headache - Flushing of the skin - Lightheadedness - Confusion - Dilated pupils
List the triggers of autonomic dysreflexia
- Distended bladder - Blocked catheter - Urinary retention - Urinary tract infection - Bladder stones - Constipation - Bowel impaction - Hemorrhoids - Skin irritation - Pressure stones - Tight clothing
Describe the treatment of autonomic dysreflexia
- Removing stimulus (tight clothing, blocked catheter, faecal impaction) - Administering antihypertensive drugs to decrease blood pressure e.g. nitrates + nifedipine
List the functions of the cardiovascular system
- Transport of nutrients, oxygen and waste products around the body - Transfer of heat (generally core->skin) - Buffer body pH - Transport of hormones - Assist in response to infection - Assist in formation of urine - filtration + circulation
Describe the heart sounds
1 = AV valves closing 2 = Pulmonary and aortic valves closing
Describe a cardiac cycle
- Systole (contraction) and diastole (relaxation) of the atria then ventricles - Blood flow controlled by valves and sequences of diastole and systole - Blood flows from area of higher pressure to one of lower pressure
Explain the differences between the left and right ventricles
Left has much thicker more muscular wall - right has to pump blood smaller distance (to lungs) than right (whole body)
Stroke volume
Volume of blood ejected from the heart per beat
Starling’s Law
The stroke volume increases in response to an increase in volume of blood in the ventricles
Equation for cardiac output
CO = SV x HR (each side)
What makes the heart contract?
- Impulses generated within the SA node spread over the atria the ventricles - SA has fastest intrinsic rate so determines heart rate - pacemaker - Atria and ventricles on left and right sides of heart contract at same time - AV node slows conduction and can act as secondary pacemaker if required - Purkinje fibres interdigitate with myocytes to spread impulse across ventricles - excitation-contraction coupling
How do ECGs work?
- Detects phasic change in potential difference between two electrodes: on surface of heart and on limbs - Recorded on oscilloscope/computer/paper
What are ECGs used for?
Diagnosis of arrhythmias, post MI damage, congenital/iatrogenic abnormalities
Describe the sections of a typical ECG
P wave = atrial depolarisation QRS complex = ventricular depolarisation T wave = ventricular repolarisation P-R interval = delay through AV node S-T interval = plateau phase of AP
Describe the process of cardiac muscle contraction
- Calcium entry into cardiac muscle cells triggers contraction - Exterior of the myocyte - Sarcoplasmic reticulum inside cell - ‘Calcium-induced calcium release’ - Allows a greater contraction for a small calcium movement - amplifier
How are changes in cardiac output detected and modulated?
- Detected by baroreceptors, information on blood pressure fed back to CVS control centre in medulla of brain - HR increased by binding of noradrenaline from sympathetic nerves and circulating adrenaline - HR decreased by action of the vagus nerve which terminates on the nodal tissue, acetyl choline released
List the types of blood vessels in the cardiovascular system
- Large arteries 2. Arterioles 3. Capillaries 4. Venules 5. Veins
Which cells line all blood vessels ?
- Endothelial cells line all blood vessel and inside of heart chambers
List the functions of endothelial cells
- Prevent platelet aggregation and blood clot formation - Permeability barrier for nutrients/fluid between plasma and interstitial fluid - Angiogenesis + vessel remodelling - Release constrictors - endothelin, thromboxane and dilators - nitric oxide, prostacyclin - Influence proliferative state if smooth muscle cells
What is the role of vascular smooth muscle?
- Present in all vessels except small capillaries - Determine vessel radius by contracting and relaxing - Secrete ECM giving vessel elastic properties
Mean arterial pressure (MAP)
Average pressure pushing blood around the system, MAP = diastolic pressure + 1/3 (systolic pressure - diastolic pressure)
Why is it important that arteries are elastic?
To allow stretching by raised blood pressure in systole
Explain how the structure of arteries and the aorta are adapted to their function
- Contain a small volume of blood at high pressure - Very thick walled/elastic
What is the function of arterioles?
- Variable resistance system which distributes the blood - Dissipates most of the pressure
Explain how the structure of capillaries is adapted to their function
- Large surface area where interchange of substances with the extracellular fluid of the tissue occurs - As little as one cell thick - Exchange of nutrients/waste products - Just wide enough for an erythrocyte to squeeze through
Explain how the structure of venules, veins and the vena cavae are related to their function
- A collecting and reservoir system containing most of the blood at low pressure - Very distensible - Veins have valves to stop back-flow due to low pressure
List the factors which control blood flow
- Length of the vessel 2. Viscosity of the blood 3. Pressure gradient across the length of the vessel 4. Cross sectional area of the vessel 5. Resistance of the vessel - proportional to diameter
What happens to blood flow as branching increases down the arterial tree?
Arteries -> arterioles -> capillaries, resistance increases, flow is reduced
How is blood flow maintained in the veins
- Valves direct blood towards heart - Skeletal muscle pump - Respiratory movements aid venous return - Sympathetic nerves - noradrenaline constricts veins = increased venous return to the heart
Preload
Venous return to the right ventricle - if preload increases the heart has to work harder to pump blood out
How can preload be reduced?
Nitrates
List the functions of the nervous system
- Communication 2. Regulating internal events 3. Organising behaviour (external) 4. Information storage (memory) 5. Sensations, perceptions, emotions
List the cells of the nervous system
- Neurones - Glia
Glia
- More numerous than neurones - Supportive, nutritional role - Myelin formation
List the types of glial cells
- Schwann cells (PNS) - Oligodentrocytes (CNS)
Neurones
- Excitable cells - Generation and transmission of signals - Synaptic processing - Various types with structure related to function
Describe the structural organisation of the nervous system
- Central nervous system - brain + spinal cord - Peripheral nervous system - spinal nerves + cranial nerves
Describe the functional organisation of the nervous system
- Sensory - afferent - Motor - efferent
List the parts of the brain
- Cerebral hemispheres 2. Cerebellum 3. Brainstem
Telencephalon
Cerebrum
Diencephalon
Thalamus,, hypothalamus
Forebrain
Telecephalon + diencephalon
Mesencephalon
Midbrain - vision, hearing, motor function, arousal state
Hindbrain
Rhombencephalon
List the parts of the cerebral hemispheres
- Frontal lobes - executive functions, long-term memory 2. Parietal lobe - integration of sensory functions 3. Occipital lobe - visual processing 4. Temporal lobe - primary auditory cortex
List the sulci of the cerebral hemispheres
- Central sulcus 2. Lateral sulcus 3. Parieto-occipital sulcus
Describe the arrangement of the spinal cord
- Dorsal roots - sensory - Ventral roots - motor - One pair of spinal nerves from each segment - Dorsal root ganglia contain cell bodies of primary sensory neurones
Nerve plexus
Peripheral nerves that supply specific body regions
Describe the functional divisions of the nervous system
- Somatic nervous system - motor and sensory - Autonomic nervous system - visceral afferent and visceral efferent (sympathetic and parasympathetic)
Afferent peripheral nerves
- Carry information to the CNS - Afferent signals in somatic nerves are associated with sensations/perceptions - Afferent signals from internal organs do not usually give rise to sensations
Efferent peripheral nerves
- Carry information away from the CNS - Cause actions e.g. muscle contraction - Somatic efferents control voluntary muscle - Visceral efferents constitute the autonomic nervous system (controlling cardiac muscle and some glands)
Describe the function of the heart
- 2 pumps, one for systemic and one for pulmonary circulation - Transporting oxygen to cells of the body and removal of waste products - Deoxygenated blood to lungs an oxygenated blood around the whole body - Must continuously beat, so is composed of cardiac muscle and myocardium made of specialised cardiac muscle cells which have their own contractile rhythm
Describe the anatomical position of the heart
- Above and on superior surface of the diaphragm - Posterior to sternum - Lies in middle mediastinum - Base is superior and to the right, apex is inferior and to the left (close to 5th intercostal space) - Anchored to diaphragm, back of sternum and great vessels by pericardium
List the great vessels
- Aorta - Pulmonary arteries - Pulmonary veins - Vena cavae
Mediastinum
Space covered with connective tissue behind the sternal body, divides the thoracic cavity into two pleural cavities
Describe the structure of the pericardium
- Two serous membrane layers - Each has epithelial lining with underlying connective tissue
What is the function of the pericardium?
- Keeps heart in place, limits motion, prevents over-expansion - Pericardial fluid between layers functions to reduce friction
Describe the layers of the pericardium
- Serosal pericardium - visceral layer and parietal layer 2. Fibrous pericardium
Serosal pericardium
- Visceral layer on outer surface of the heart wall - Parietal layer on deep surface of the fibrous pericardium - Between layers is pericardial cavity, filled with pericardial fluid
Fibrous pericardium
- Superficial layer of the pericardium - Composed of dense irregular connective tissue - Attaches to parietal layer of serous pericardium, encloses the heart - Attached below to diaphragm and above to the great vessels of the heart - Function = limits motion of the heart, resists stretch to stop heart from over expanding
List the layers of the heart wall
From inside -> outside 1. Endocardium 2. Myocardium 3. Epicardium
Endocardium
- Smooth, thin membrane lining the inner surface of the heart chambers - Composed of a layer of endothelial cells, lies over a layer of connective tissue - Covers valves of the heart - Helps prevent resistance as blood passes through heart
Myocardium
- Heart muscle - Varies in thickness depending on location - thin in atria, thick in ventricles - Composed of cardiac muscle fibres, exhibit striations diagonally across heart
Epicardium
- Outer serous membrane of heart wall - Same as inner layer of serous pericardium (visceral pericardium) - Composed mainly of connective tissue mesothelial cells - Gives a smooth texture on the outer surface of the heart
List the chambers of the heart
- Right atrium 2. Right ventricle 3. Left atrium 4. Left ventricle
Right atrium
- Small, thin walled chamber - Receives deoxygenated blood from entire body via superior and inferior vena cava - Receives blood from myocardium through the coronary sinus
Describe the function of the right atrium
Pumps deoxygenated blood from the atrioventricular (tricuspid) valve into the right ventricle
Left atrium
- Small, thin walled chamber - Forms the base of the heart - Receives oxygenated blood from the lungs via the four pulmonary veins
Describe the function of the left atrium
Pumps oxygen-rich blood from the atrioventricular (bicuspid) valve into the left ventricle
Atria
- Two upper chambers of the heart, positioned near its base - Have small semi-elastic pouches called auricles, that expand when filled with blood - Auricles ensure there is sufficient blood volume to permit maximal contraction of the ventricles - Atrial walls are thin as they only have to squeeze blood past the AV valves into their corresponding left or right ventricles
Ventricles
- Two lower chambers of the heart positioned near its apex - Walls are thicker than atria and wall of left ventricle is especially thick - has to push blood at high pressure around the entire body
Right ventricle
- Thick walled chamber that forms most of the anterior surface of the heart - Receives deoxygenated blood through tricuspid valve from right atrium
Describe the function of the right ventricle
Pumps deoxygenated blood into the the lungs from the pulmonary valve and trunk
Left ventricle
- Thickest walled chamber - Cone-shaped - Forms most of back and lower surface of the heart - Receives oxygenated blood through the bicuspid valve into left atrium
Describe the function of the left ventricle
Pumps oxygenated blood to the entire body through the aortic valve via the aorta
Septum of the heart
Muscular septum - divided into interatrial septum and interventricular septum
Interarterial septum
Separates the left and right atria
Interventricular septum
Divides the left and right ventricles
Fossa ovalis
Small depression on the interatrial septum, the embryonic remnant of the foramen ovale - an opening in the fetal heart which closes shortly after birth
What separates the atria from the ventricles?
Shallow grooves on the external surface of the heart called sulci
List the sulci of the heart
- Coronary sulcus - Anterior interventricular sulcus - Posterior interventricular sulcus
Coronary sulcus
- Groove on the external surface of the heart - Marks the division between the superior atria and inferior ventricles - Contains the trunks of the coronary vessels and coronary sinus
Anterior interventricular sulcus
- Shallow groove on sternocostal, anterior surface of the heart - Marks the division between right and left ventricles - Contains the branch of the left coronary artery
Posterior interventricular sulcus
- Shallow groove on the diaphragmatic, posterior surface of the heart - Marks the division between right and left ventricles - Contains the posterior interventricular artery and the middle cardiac vein
Cardiac skeleton
Dense layer of connective tissue which connects the atria and ventricles. Serves as an insertion point for cardiac muscle fibres, provides electrical insulation through the atrioventricular node from right atria to right ventricle. Gives structural stability in the form of rings of connective tissue that surround the valves of the heart.
List the valves of the heart
- Pulmonary valve 2. Aortic valve 3. Right atrioventricular valve (tricuspid valve) 4. Left atrioventricular valve (bicuspid valve)
How do the valves of the heart work?
Open and close in response to pressure created by the volume of blood as it is pumped into each chamber as the heart contracts
What is the function of the atrioventricular valves?
Located between the atria and ventricles and prevent the blood in the ventricles from flowing back into the atria. Closing of the AV valves creates the first heart sounds - ‘lub’.
Right atrioventricular valve (tricuspid)
- Lies between the right atrium and right ventricle - Also known as tricuspid valve - because it has three cusps - Chordae tendinae attached to inferior portion of the cusps
Chordae tendinae
- Thin, string like structures attached to the inferior portion of the atrioventricular valves - Attached to the ventricular wall or papillary muscles - They prevent the valve prolapsing into the atria - Prevent the back-flow of blood from the ventricles into the atria during ventricular systole
Left atrioventricular valve (biscuspid)
- Lies between the left atrium and left ventricle - Known as mitral valve or bicuspid valve because it has two cusps - Chordae tendinae attached to inferior portion of cusps
Semilunar valves
- Prevent the back flow of blood from the pulmonary trunk and the aorta to the right ventricle and left ventricle - Have three crescent-shaped cusps - When ventricles contract, cusps of valves are pushed flat against the walls of the vessels, keeping the valves open - When the ventricles stop contracting, the blood immediately tries to flow back in the opposite direction - into ventricles - Returning blood flows into the cusps of the valves, opening them out and blocking the flow of blood back into the ventricles