Efferent Division: Autonomic and Somatic Motor Control Chapter 11 Efferent Division: Autonomic and Somatic Motor Control

About this Chapter Efferent division and what it controls Pathways receptors and neurotransmitters Antagonistic controls: sympathetic and parasympathetic Control of cardiac, smooth muscle, some adipose tissue and glands in homeostasis CNS control of skeletal muscles through neuromuscular junctions

Autonomic Division: Homeostatic balancing Controls Smooth & cardiac muscle Glands & adipose Antagonistic branches Parasympathetic "Rest & digest" Restore body Sympathetic "Fight or flight" Energetic action

Autonomic Division: Homeostatic balancing Figure 11-1: Homeostasis and the autonomic division

Autonomic Control Centers Hypothalamus Water balance Temperature Hunger Pons Respiration Cardiac Vasoconstriction Medulla Figure 11-3: Autonomic control centers in the brain

Autonomic Pathways: Communicate to Body Coordinates homeostatic responses Autonomic Endocrine Behavioral Blood pressure Osmolarity Tonic regulation Antagonistic control Receptor directed response

WHAT IS ROHHAD? ROHHAD is an acronym for rapid-onset obesity with hypothalamic dysregulation, hypoventilation and autonomic dysregulation. It affects the part of the nervous system that controls involuntary actions and the endocrine system. Scientists suspect the condition is genetic but are still unsure. The disease is incredibly rare, and less than 100 people in the world have been diagnosed with it.  Signs and symptoms: Dramatic weight gain over a six to 12-month period Inability to maintain normal water balance in the body Inability to regulate body temperature Slow heartbeat and excessive sweating Very shallow breathing during sleep There is currently no cure for ROHHAD, with the average life expectancy being between five and nine, reports suggest. Because it can affect many different parts of the body, children are often cared for by a team of healthcare providers from various fields. The weight gain is often hard to control through exercise and diet - but keeping active helps to avoid excess from being piled on.

Autonomic Pathways: Communicate to Body Figure 11-2: The hypothalamus and brain stem initiate autonomic, endocrine, and behavioral responses

Autonomic Pathways: Two Efferent Neurons CNS Preganglionic neuron Ganglion Postganglionic neuron Target tissue Figure 11-4: Autonomic pathways

Comparison of sympathetic and Parasympathetic Pathways Neurotransmitters Receptors Figure 11-7: Sympathetic and parasympathetic pathways

Parasympathetic Branch: “Rest and Digest” Preganglionic neurons Originate in Brain stem Lower cord NT: cholinergic Ganglion Near target Nicotinic receptors Postganglionic neuron

Figure 11-5: Autonomic sympathetic and parasympathetic pathways

Actions of Parasympathetic Branch Constricts Pupil Bronchioles Slows heart Stimulates Digestion Insulin release Urination Erections

Sympathetic Branch: “Fight or Flight” Preganglionic neuron Short Origin: spinal cord NT: cholinergic Ganglia Sympathetic chain Near spinal cord Postganglionic neuron Long NT: adrenergic

Homeostasis Hypothalamus: Homeostatic Functions Hunger, stress Thirst: body osmolarity Flight/fight pathways Anger & fear Circadian rhythms Coordinates with endocrine system

Additonal Functions of Hypothalamus heart rate urinary bladder contraction blood pressure oxytocin release vasopressin release corticotropin-releasing hormone release[8] thermoregulation panting sweating thyrotropin inhibition GI stimulation satiety neuroendocrine control Gonadotropin-releasing hormone (GNRH), also known as Luteinizing-hormone-releasing hormone(LHRH) pupillary dilation shivering

Examples of Autonomic Reflexes Cold Water (Whole Body) Immersion causes tachycardia Exposure of face to cold water causes bradycardia: Mammalian Diving Reflex via Vagal Nerve Pupillary Reflex-Pupil Constricting in response to light Baroreceptor Reflex- Low BP in carotid sinus results in tachycardia and blood vessel constriction Carotid Sinus Reflex- Increased pressure within or external manipulation of carotid sinus results in bradycardia Dilation of Blood vessels as body temperature increases Secretion of epinephrine and norepinephrine from the adrenal medulla in response to fear or stress Sweating in response to increased body temperature

Autonomic Effects on Cardiovascular System Target Sympathetic (adrenergic) Parasympathetic (muscarinic) cardiac output β1, (β2): increases M2: decreases SA node: heart rate (chronotropic) β1, (β2) [4]: increases Atrial cardiac muscle: contractility (inotropic) β1, (β2)[4]: increases at AV node β1: increases conduction increases cardiac muscle automaticity [4] M2: decreases conduction Atrioventricular block [4] Ventricular cardiac muscle β1, (β2): increases contractility (inotropic) increases cardiac muscle automaticity [4] --- Heart

Autonomic Effects on Blood Vessels Target Sympathetic (adrenergic) Parasympathetic (muscarinic) vascular smooth muscle in general α1:[5] contracts; β2:[5] relaxes M3: relaxes [4] renal artery α1[6]: constricts --- larger coronary arteries α1 and α2[7]: constricts [4] smaller coronary arteries β2:dilates [8] arteries to viscera α: constricts arteries to skin arteries to brain α1[9]: constricts [4] arteries to erectile tissue α1[10]: constricts M3: dilates arteries to salivary glands hepatic artery β2: dilates arteries to skeletal muscle Veins α1 and α2 [11] : constricts β2: dilates Blood vessels

Stimulatory Actions of Sympathetic Branch Pupil dilation Salivation Heart beat & volume Dilation Blood vessels Bronchioles Catecholamine release Fat breakdown Ejaculation

Inhibitory Actions of Sympathetic Branch Digestion Pancreas secretion Urination

Adrenal Medulla: A Modified Sympathetic Ganglion Sympathetic stimulation Catecholamine release to blood Epinephrine Norepinephrine Travel to: Multiple targets Distant targets

Adrenal Medulla: A Modified Sympathetic Ganglion Figure 11-10: The adrenal medulla

Synapses in Autonomic Nerves Varicosities NT released to ECF No cleft Impact Large area Slow acting Long duration Figure 11-8: Varicosities of autonomic neurons

Mechanism: Norepinephrine Release and Recycling Figure 11-9: Norepinephrine release at a varicosity of a sympathetic neuron

Review of Efferent Pathways: Motor & Autonomic Figure 11-11: Summary of efferent pathways

Somatic Motor Division: Controls Skeletal Muscles Body movement Appendages Locomotion Single neuron CNS origin Myelinated Terminus Branches Neuromuscular junction Figure 11-11: Summary of efferent pathways

Neuronmuscular Junction: Overview Terminal boutons Synaptic cleft Filled with a fibrous Matrix (collagen) AChE Hold axon terminal and motor end plate together Motor end plate On muscle Nicotinic receptors

Neuronmuscular Junction: Overview Figure 11-12: Anatomy of the neuromuscular junction

Neuronmuscular Junction: Mechanism of Signal Conduction Axon terminal AP signals ACh release Motor end plate 2 ACh bind opens cation channel Na+ influx Membrane depolarized Stimulates fiber contraction

Neuronmuscular Junction: Mechanism of Signal Conduction Figure 11-13: Events at the neuromuscular junction

Summary Autonomic branches: sympathetic and parasympathetic Regulate glands, smooth & cardiac muscles Team with endocrine to regulate homeostasis Are regulated by hypothalamus, pons & medulla Have pathways with 2 neurons and a ganglion Use varicosities to release NTs Have diverse receptors: tonic & antagonistic regulation

Summary Efferent motor neurons control skeletal muscles Single long myelinated neuron from CNS Neuromuscular junction structure & mechanism