Chapter 13 Part 2 (2) PDF - Biology

Limbic system (“limbus” = border) Consists of various structures forming a ring around the diencephalon along the inner border of the cortex + some internal structures  Some Functions of the Limbic System: - processes and experiences emotions: pain, pleasure, docility, control of beha...

Limbic system (“limbus” = border) Consists of various structures forming a ring around the diencephalon along the inner border of the cortex + some internal structures  Some Functions of the Limbic System: - processes and experiences emotions: pain, pleasure, docility, control of behaviors responsible for affection, anger, involved in self- the long-term addiction, sexual preservation: fear memory attraction and aggression formation Spinal cord The spinal cord features : C1 C2 Atlas C3 Cervical 1. Extends inferiorly from the part C4 C5 Cervical C6 brain through the vertebral canal C7 enlargement C8 T1 and ends at the level of L1 T2 T3 T4 vertebra. T5 T6 Thoracic T7 part T8 2. Roughly cylindrical with the T9 T10 anterior median fissure (deep) Lumbosacral T11 Lumbar enlargement and posterior median sulcus Conus T12 part Sacral (shallow) L1 medullaris L2 part L3 L4 Cauda L5 equina S1 3. Encapsulated by the spinal cord S2 S3 S4 meninges continuous with cranial S5 Co1 meninges (dura mater, arachnoid mater, pia mater) (a) Posterior view 4. Coming off the spinal cord: rootlets  dorsal (sensory) and ventral (motor) roots  31 pairs of spinal nerves Dorsal root Dorsal horn (sensory) (interneurons) Dorsal root ganglion Spinal nerve Ventral root Ventral horn (motor) (motor neurons) 5. There are two major functions of the spinal cord due to the grey and white matter. A. signal integration: gray matter receives and processes incoming and outgoing information B. signal propagation: white matter serves as a highway for travelling sensory and motor signals Spinal cord is an integration center for some reflexes Reflex - rapid, pre-programmed, involuntary reaction of a muscle or a gland to a certain stimulus. Reflex arc – is a neural pathway that controls a single reflex, its neural “wiring”: 1. Stimulus 2. Nerve signal is 3. The nerve signal is processed activates a____. propagated through in the integration center by the the ____neuron to ______neurons. Skin the spinal cord. Interneuron 4. Nerve signal is 5. ___ (muscle or propagated by the ____ gland) responds. neuron to the effector. Monosynaptic reflexes Polysynaptic reflexes (simplest) - sensory axons have more complex neural pathways directly synapsing on motor (with one or more interneurons) => neurons with very minor they exhibit prolonged synaptic delay synaptic delay before response e.g., patellar reflex e.g., withdrawal reflex Sensory (stretch) receptor Spinal cord Sensory receptor Sensory Sensory neuron neuron Interneuron Effector organ Effector organ Motor neuron Motor neuron A clicker question follows… 5. There are two major functions of the spinal cord due to the grey and white matter. A. signal integration B. signal propagation White matter is partitioned into Posterior column three regions (columns). Lateral column Anterior column Axons within each column are organized into smaller tracts or to conduct either sensory or motor signals. Sensory (ascending) pathways Primary somatosensory cortex (postcentral gyrus) - deliver signals from the ________ Cerebrum to the brain in order to inform about Tertiary the changes in internal and external Thalamus neuron environment. Most are composed of ____ neurons: Midbrain primary, secondary, and tertiary neurons Secondary Pons neuron Most arrive to the thalamus primary somatosensory cortex. Medulla oblongata Receptors for pain, temperature, crude touch, pressure Primary neuron Spinal cord  Pathway direction Primary motor cortex (precentral gyrus) Cerebrum Motor (descending) pathways Upper Deliver signals from the brain to motor the various _______ or ________ neurons in order to cause a response: excitation/inhibition. Midbrain Most are composed of ____motor neurons: upper and lower. Medulla oblongata To skeletal muscles Lower motor neurons Clicker question follows… Spinal cord Chapter 9 Chapter 9 Chapter 9  Chapter 9 Autonomic: (cardiac muscle, smooth muscle and glandular involuntary control). - 2 motor neuron system (slower) - motor neurons leaving the spinal cord do NOT innervate the effector tissue directly. They first synapse with a second motor neuron which makes contact with the tissue. - The synapse occurs within an autonomic ganglion (collection of cell bodies). - The first motor neuron, that runs from the spinal cord to the ganglion is the preganglionic neuron. - The postganglionic neuron, leaves the autonomic ganglion and innervates the effector tissue. Chapter 9  Chapter 9 Divisions of the autonomic nervous system: I. Sympathetic “Fight or Flight” division: Spinal Cord Exit – Thoracolumbar (T1-L2) LONG – Postganglionic neurons Preganglionic motor neurons leave the ventral horn of the spinal cord via the ventral root to join the afferent neurons in the spinal nerve. However, the sypmpathetic axons exit the spinal nerve via a white rami communicantes to enter one of the sympathetic ganglia that are arranged and linked into the sympathetic chain of ganglia. Some preganglionic fibers branch and send fibers to other ganglia along the levels of the body Chapter 9  Chapter 9 The Pre- and Postganglionic neurons synapse within the ganglion and unmyelinated axons exit the ganglion via a grey rami communicantes to re-enter the spinal nerve en route to the effector organs. Some Preganglionic neurons send their axons past the chain of ganglion through splanchnic nerves and form synapses with post ganglionic neurons in collateral ganglia. T5-T9 = greater splanchnic nerve (for upper abdomen; liver, stomach, small intestine, pancreas, adrenal gland, upper portion of large intestine. T10-T12 = lesser splanchnic nerve (lower large intestine, kidney Chapter 9  Chapter 9 Sympathetic collateral ganglia: Celiac - These unmyelinated postganglionic axons innervate the stomach, liver, gallbladder, spleen, kidney, small intestine, and the ascending and transverse colon. superior mesenteric - These unmyelinated postganglionic axons are distributed to all the parts supplied by the superior mesenteric artery: the pancreatic branches to the pancreas; intestinal branches to the small intestine; and ileocolic, right colic, and middle colic branches, which supply the corresponding parts of the large intestine. inferior mesenteric - These unmyelinated postganglionic axons are distributed to all the parts supplied by the inferior mesenteric artery: the left colic and sigmoid plexuses, which supply the descending and sigmoid parts of the colon; and the superior hemorrhoidal plexus, which supplies the rectum and joins in the pelvis with branches from the pelvic plexuses. Chapter 9  Chapter 9 Ia. Sympathoadrenal system: Chromaffin cells in the adrenal medulla are stimulated by preganglionic neurons (greater splanchnic nerve) to release epinephrine (85%) and norepinephrine (15%) into the blood stream (functions as postganglionic neurons).  Chapter 9 II. Parasympathetic “rest and digest “division: Spinal Cord Exit – Craniosacral: - Cranial nerves: - S2-S4 – Pelvic nerves; lower colon, rectum, bladder and reproductive organs. Chapter 9  Chapter 9 II. Parasympathetic “rest and digest “division: Spinal Cord Exit – Craniosacral: - Cranial nerves: - III (Oculomotor nerve, M – iris and ciliary muscle) - VII (Facial, B – nasal mucous glands, lacrimal glands and salivary glands) - IX (Glossopharyngeal, B – parotid gland) - X (Vagus, B – heart, lungs, GI tract, liver, pancreas) - S2-S4 – Pelvic nerves; lower colon, rectum, bladder and reproductive organs. Chapter 9  Chapter 9 LONG – preganglionic neurons. Pre- Postganglionic synapses occurring either in the effector organ or near the organ in terminal ganglia (very short postganglionic neurons). Ciliary - Oculomotor nerve Pterygopalatine – Facial nerve (nasal mucosa and lacrimal glands) Submandibular – Facial nerve (salivary glands) Parotid – Glossopharyngeal Chapter 9  Chapter 9 Functions of Autonomic Nervous system Sympathetic Target Parasympathetic Increased rate and strengthHeart decreased rate Dilate pupil Iris constrict pupil Constriction (of most) Blood vessels dilation in only a few Dilation Bronchioles (lungs) Constriction GI tract Stomach Stimulate secretion Inhibit movement Motility Stimulate Closed Sphinctersmovement Chapter 9  Chapter 9 Neurotransmitters used in the Autonomic Nervous system Cholinergic : - all preganglionic neurons (sym- and para-) – always excitatory - all para- postganglionic neurons – mostly excitatory (those to heart inhibit and slow heart rate). - (some sym- post- neurons to blood vessels of muscles and sweat glands) – mostly excitatory. Chapter 9  Chapter 9 Receptors: Nicotinic – always excitatory (ligand-gated ion channel) Muscurinic – can be either inhibitory or excitatory (G protein signaling) Chapter 9  Chapter 9 Adrenergic : Most postganglionic sym- neurons (see exceptions under cholinergic) – can be excitatory or inhibitory. Ex. Heart rate increases upon excitatory stimulation Ex. Smooth muscles of bronchioles are inhibited (leads to dilation). Chapter 7  Chapter 9 Receptors: (all are G-protein coupled) a1 – signals via Ca2+ influx similar to cAMP signaling. Constriction of vascular smooth muscle. a2 – these are present in presynaptic membranes (negative feedback); vascular smooth muscle (post synaptic membrane) leading to vasoconstriction; in brain, leads to reduced activity for the entire sympathetic nervous system. b - both 1 and 2 subtypes signal via cAMP cascade. 1 – stimulates heart to increase force and rate 2 – relaxes smooth muscle in GI tract, bronchioles and uterus Chapter 9