Week 1: Tuesday Flashcards
what does the autonomic nervous system do
- innervates viscera - unconscious control
- mediates homeostasis
- visceral sensory and visceral motor neurons that function in visceral reflexes
- takes 2 motor neurons in series to innervate organs
- parasympathetic and sympathetic
- dual innervation of organs
what is homeostasis
maintenace of critical physiological parameters of the internal environment within the limits comparible with life
what are the functions of the parasympathetic divistion
- conserves and restores energy reserves (anabolic)
- promotes digestion, absorption, and storage
- protective - miosis - contriction of pupil
- rest and digest
where does the parasympathetic nervous system originate
- from a restricted part of brain and spinal cord (cranial-sacral)
- has own set of peripheral ganglia
what are the functions of the sympathetic division
- prepares body for action
- mobilizes energy stores (catabolic)
- mediates responses to stress
- fight or flight
where does the sympathetic nervous system originate
- from restricted part of spinal cord (thoracolumbar)
- has own set of peripheral ganglia
what is dual innervation
- many organs have a sympathetic and a parasympathetic innervation (one excites and other inhibits)
- some organs don’t (skin, sweat glands, arrector pili muscle, vascular smooth muscle, adrenal gland and adipose tissue) - only sympathetic
resting membrane potential
- net negative charge inside the cell membrane
- ion pumps maintain concentration gradient
what are contractile cardiac cells
- generate force
- not autorhythmic, but do conduct action potentials
what are autorhythmic cardiac cells
- provide a pathway for spreading excitation through the heart (pacemaker cells, conduction fibers)
- don’t generate much contractile force
what are fast-response action potentials
- contractile cardiac cells
- Na+ driven (fast Na+ channels)
what are slow-response action potentials
- autorhythmic cardiac cells
- Ca2+ driven (L-type Ca2+ channels)
- pacemaker potentials lead to spontanous action potentials
- due to hyperpolarization-activated cyclic nuceotide-gated (HCN) channels (funny current) and T-type calcium channels
what are the 3 steps in action potentials in contractile cardiac cells
- rapid depolarization
- plateau
- repolarization
what are the 6 important membrane currents in contractile cardiac cells
- INa: sodium current
- ICa: L-type Ca current
- Ito: transient outward K current
- IKr: rapidly activated delayed rectifying K current
- IKs: slowly activating delayed rectifying K current
- IK1: inward rectifying K current
what membrane currents are in phase 4 of autorhythmic cells
- If: funny current, HCN channel
- ICa2+ (T): T-type voltage gated channel
what membrane currents are in phase 0 of autorhythmic cells
ICa2+ (L): L-type voltage gated channel
what phases are absent in autorhythmic cells
phase 1 and 2
what membrane currents are in phase 3 of autorhythic cells
IK: potassium current, dlayed rectifier potassium
what membrane current is important for parasympathetic regulation of HR
IKACh: rectifying potassium current
what happens at intercalated disks
- desmosomes provide structural strength
- cells linked by gap junctions
what do gap junctions allow the cell to behave as
a functional syncytium
during a heartbeat where is the first action potential initiated
the SA node
what is the AV node
the only pathway through which the signal can pass between the atria and ventricles
slight delay from SA to AV node
why is there a delay between the SA and AV node
reduction of gap junctions and reduction of diamter of cells
