Lecture 5: Neurophysiology Pt 4 Flashcards
What is the purpose of the autonomic nervous system (ANS)?
-Autonomic= controls body functions w/o conscious thought (automatically, involuntary), key in maintenance of homeostasis, accomplished by automatic reflexes
-Controls smooth muscle, cardiac muscle, and glands (directly controls: reparation, heart rate, BP, digestions, rumination, sleep, arousal, body temp
-Reflex=sensory cells, sensory nerve fibres, integration center, motor nerve fibre, effector (same bc reflex always involves these 5 things)
How is the reflex similar to somatic nerve reflex and how is it different?
Sensory cells: spend on the system considered (cold, warm etc)
Sensory nerve fibres: No major difference from somatic
Control centers:
-Hypothalamus: master command
-Brain stem: special control function (respiratory centre)
-Spinal cord: Local integration in thoracic and scrap segments
-Receives continuous info from sensory nerves (frequent impulses)
-Compare info to set pt –>if different alter frequency on the motor fibre
Motor nerve fibre: big difference from somatic
-Target organ (smooth muscle, cardiac muscle, glands)
-# of neurons in its peripheral circuit
-2 peripheral nerves (VS 1 somatic arc reflex)
-Preganglionic Neuron-cell body in the CNS with axon that innervates a second neuron the postganglioic neuron
-Cell body of the postganglionic neuron is in a ganglion
What are the 2 major divisions of the ANS?
Sympathetic (thoracic-lumbar) ALARM
-Activated during stress (can be internal, something that can put body in danger)
-Preganglionic neurons originate in thoracic or lumbar spinal area and send axons to sympathetic ganglia which forms a chain parallel to the spinal cord
-All ganglion in SNS are interconnected that why if you have a stressor ex pop test allows system to have a shared response sweat, high blood pressure)
Parasympathetic (croanio-sacral)
-Most active during rest controls REST
-preganglionic neurons originate in the brain or sacra part of the spinal cord and send axons to ganglia near or within effector organs
Enteric Nervous system: Branch of parasympathetic, digestion and rumination
Where is the outflow from for the SNS?
The outflow from thoracolumbar spinal cord–> preganglionic axons enter the paravertebral sympathetic ganglion chain
-postganglionic fibers are very long (innervate hollow organs, blood vessels etc)
-Some preganglionic fibres extend to the adrenal medulla and simulate the secretion of epinephrine and norepinephrine into blood circulation
Where is the outflow from the PNS?
very long preganglionic fibers
-cranial nerves 3,7,9,10 supply parasympathetic fibres to body’s glands and organs
-#10=vagus nerve-major supplier to the body
Ganglia
-Located in wall or adjacent to target organ
-No interconnection b/w ganglia
Postganglionic fibers = short axons
-direct connection with specific organs (no branching off) with no enhancement by hormones= Selective action
What are receptors to acetylcholine?
Nicotinic:
-preganglionic synapses
-(neuromuscular junctions = skeletal muscle not ANS)
-Ionotropic = part of an ion channel (here Na+)
Muscarinic
-In target organs of parasympathetic
-Seperate from ion channel–> requires intracellular second messengers to activate target cell
-Depending on messenger can be inhibitory or stimulatory
-Slower and more prolonged effect then nicotinic
What are the receptors to (nor)adrenalin (adrenergic)?
-Separate receptors associated to G-proteins–> active intracellular second messenger
-Alpha-adrenergic
a1=Increase Ca2+
a2=Dcrease Ca2+
Usually construction o smooth muscles (vascular)
-beta-adrenergic
b1 and b2= increase cAMP
-main form in the heart increase contraction strength and rate
-relaxation of smooth muscles (DI tract, uterus, bronchioles)
What is the pharmacological significance of alpha and b?
-use of agonists and antagonists to selectively activate or block receptors
-hypertension
-Asthma
-Atropine
