Fundamentals of Anatomy & Physiology Chapter 14: The Brain and Cranial Nerves PDF

Fundamentals of Anatomy & Physiology Eleventh Edition Chapter 14 The Brain and Cranial Nerves © 2018 Pearson Education, Inc.  14-1 The Brain ▪ Large, delicate mass of neural tissue – Containing internal passageways and chambers filled with ce...

Fundamentals of Anatomy & Physiology Eleventh Edition Chapter 14 The Brain and Cranial Nerves © 2018 Pearson Education, Inc.  14-1 The Brain ▪ Large, delicate mass of neural tissue – Containing internal passageways and chambers filled with cerebrospinal fluid ▪ Each of the six major brain regions has specific functions – Ascending from the medulla oblongata to the cerebrum, brain functions become more complex and variable ▪ Conscious thought and intelligence – Produced in the neural cortex of the cerebral hemispheres © 2018 Pearson Education, Inc.  14-1 The Brain ▪ Cerebrum – Largest part of adult brain – Controls higher mental functions Conscious thoughts, intellect, memory, etc. – Divided into left and right cerebral hemispheres 3 © 2018 Pearson Education, Inc.  14-1 The Brain ▪ Cerebellum – Second-largest part of brain – Coordinates repetitive body movements – Proprioceptor info sent here – Two hemispheres – Covered by gray matter (cerebellar cortex) 4 © 2018 Pearson Education, Inc.  14-1 The Brain ▪ Diencephalon – Located under cerebrum and above cerebellum – Links cerebrum with brain stem – Three divisions of the diencephalon 1. Left thalamus 2. Right thalamus 3. Hypothalamus © 2018 Pearson Education, Inc.  14-1 The Brain Diencephalon ▪ Thalamus – Relays and processes sensory information ▪ Hypothalamus – Connects endocrine and nervous system Hormone production Emotion Autonomic function © 2018 Pearson Education, Inc.  14-1 The Brain Diencephalon ▪ Pituitary gland – Major endocrine gland – Attached to hypothalamus via infundibulum (stalk) – Interfaces nervous and endocrine systems © 2018 Pearson Education, Inc.  Extra Information- You’ll see this in AP2 8 © 2018 Pearson Education, Inc.  14-1 The Brain ▪ Brainstem – Process information between spinal cord and cerebrum or cerebellum – Includes Midbrain Pons Medulla oblongata https://www.verywellhealth.com/brainstem-anatomy-5095691 9 © 2018 Pearson Education, Inc.  14-1 The Brain ▪ Midbrain (Mesencephalon) – Processes sight, sound, and associated reflexes Ex: responses to loud sounds – Maintains consciousness ▪ Pons – Connects cerebellum to brainstem – Contains Tracts Involved in somatic and visceral motor control 10 © 2018 Pearson Education, Inc.  14-1 The Brain Brain Stem ▪ Medulla oblongata (“Primitive brain”) – Connects brain to spinal cord – Relays sensory information – Regulates autonomic functions Heart rate, blood pressure, and digestion MEDical equipment to monitor heart rate, oxygen level, etc. 11 © 2018 Pearson Education, Inc. Figure 14–1 An Introduction to Brain Structures and Functions (Part 2 of 2). c Diencephalon Thalamus Relays and processes sensory information Hypothalamus Controls emotions, autonomic functions, and hormone production d Midbrain Brainstem Processes visual and auditory data Generates reflexive somatic motor responses Maintains consciousness e Pons Relays sensory f Medulla oblongata information to cerebellum and Relays sensory information to thalamus and thalamus to other portions of the brainstem Subconscious Autonomic centers for regulation of visceral somatic and visceral function (cardiovascular, respiratory, and motor centers digestive system activities) 12  14-2 Brain Protection and Support ▪ Physical protection – Bones of the cranium – Cranial meninges – Cerebrospinal fluid ▪ Biochemical isolation – Blood brain barrier Astrocytes Millions of head injuries every year, but only one case in eight results in serious brain damage. 13 © 2018 Pearson Education, Inc.  14-2 Brain Protection and Support ▪ Cranial meninges – Three layers: Dura mater Arachnoid mater Pia mater – Continuous with spinal meninges – Protects the brain from cranial trauma 14 © 2018 Pearson Education, Inc.  14-2 Brain Protection and Support ▪ Cranial meninges – Dura mater Inner fibrous layer (“meningeal layer”) Outer fibrous layer (“periosteal layer”) – Fused to periosteum Dural Venous sinuses between inner and outer layers 15 © 2018 Pearson Education, Inc. https://antranik.org/protection-for-the-brain-meninges-csf-blood-brain-barrier/  14-2 Brain Protection and Support ▪ Cranial meninges – Arachnoid mater Covers brain with a smooth sheet Attaches to dura mater – But may be separated by subdural space* due to trauma, disease, or lack of CSF ex. Cadaver Subarachnoid space lies between arachnoid mater and pia mater – Pia mater Attached to brain surface by astrocytes Follows grooves and structures of brain 16 © 2018 Pearson Education, Inc.  14-2 Brain Protection and Support ▪ Dural folds – Folded inner layer of dura mater into cranial cavity Stabilize and support brain (i.e., Seatbelt) – Contain collecting veins (dural venous sinuses) Veins of brain open into sinuses – Three largest dural folds Falx cerebri Tentorium cerebelli Falx cerebelli 17 © 2018 Pearson Education, Inc.  14-2 Brain Protection and Support ▪ Falx cerebri – Projects between cerebral hemispheres – Contains superior sagittal sinus and inferior sagittal sinus ▪ Tentorium cerebelli – Separates cerebrum from cerebellum – Contains transverse sinus allows blood to drain from back of head ▪ Falx cerebelli – Divides cerebellar hemispheres below the tentorium cerebelli 18 © 2018 Pearson Education, Inc. Figure 14–3a The Relationships among the Brain, Cranium, and Cranial Meninges. Cranium Periosteal cranial dura Dura mater Dural sinus Subarachnoid space Meningeal cranial dura Pia mater Subdural space Cerebral cortex Arachnoid mater Cerebrum Cerebellum Medulla oblongata Spinal cord a A lateral view of the brain, showing its position in the cranium and the organization of the meninges 19 Figure 14–3b The Relationships among the Brain, Cranium, and Cranial Meninges. Dura mater Superior sagittal Cranium Inferior sagittal sinus sinus Dural folds Falx cerebri Tentorium cerebelli Falx cerebelli Dura mater follows fissures in the brain Transverse sinus b A diagrammatic view, showing the orientation of the three largest dural folds: the falx cerebri, tentorium cerebelli, and falx cerebelli 20  14-2 Brain Protection and Support ▪ Cerebrospinal Fluid (CSF) – Surrounds all exposed surfaces of CNS – Interchanges with interstitial fluid of brain – Functions of CSF Supports brain weight Cushions neural structures from physical trauma – i.e.. Airbag Transport nutrients, chemical messengers, and wastes 21 © 2018 Pearson Education, Inc.  14-2 Brain Protection and Support ▪ CSF circulates: – From choroid plexus Through ventricles – To central canal of spinal cord Into subarachnoid space ▪ via two lateral apertures and one median aperture around the brain, spinal cord, and cauda equina – “apertures” = exits © 2018 Pearson Education, Inc.  14-2 Brain Protection and Support Cerebrospinal Fluid (CSF) ▪ Choroid plexus – Specialized ependymal cells and capillaries Secrete CSF into ventricles Remove waste products from CSF Adjust composition of CSF at capillaries – Proteins, ions, lipids, amino acids, etc. – Different than blood – Produces about 500 mL of CSF/day © 2018 Pearson Education, Inc.  14-2 Brain Protection and Support Cerebrospinal Fluid (CSF) ▪ CSF in subarachnoid space – Arachnoid villi Extensions of subarachnoid membrane Extend through dura mater to superior sagittal sinus – Arachnoid granulations (in adults) Large clusters of villi CSF absorbed into venous circulation ▪ Hypercephaly – “water on the brain” © 2018 Pearson Education, Inc. Figure 14–4 Formation and Circulation of Cerebrospinal Fluid (Part 1 of 3). Nutrients, Interstitial fluid O2 in thalamus Capillaries Wastes, Neuron CO2 Astrocyte Choroid plexus 1 ependymal cells Ependymal cells The choroid plexus produces and maintains CSF. Two extensive folds of the choroid plexus originate Removal in the roof of the third ventricle and extend through of waste the interventricular foramina. These folds cover the floors of the lateral ventricles. In the inferior Production Cerebrospinal brainstem, a region of the choroid plexus in the of CSF fluid in third roof of the fourth ventricle projects between the ventricle cerebellum and the pons. Tight junction Choroid plexus Ions, hormones, proteins, messengers, etc. dissolved in blood plasma. Only plasma, not other “stuff” cross into CSF 25 Concentrations differ between CSF and blood Figure 14–4 Formation and Circulation of Cerebrospinal Fluid (Part 2 of 3). Choroid plexus of third ventricle Choroid 2 plexus The CSF circulates from the choroid plexus through of fourth the ventricles and fills the ventricle central canal of the spinal cord. As it circulates, 3 The CSF reaches the materials diffuse between subarachnoid space the CSF and the interstitial through two lateral fluid of the CNS across the apertures and a single ependymal cells. median aperture in the roof of the fourth Spinal cord ventricle. Central canal 4 Dura mater Cerebrospinal fluid then flows through the Conus medullaris subarachnoid space surrounding the brain, Arachnoid mater spinal cord, and cauda equina. Cauda equina Filum terminale 26 Figure 14–4 Formation and Circulation of Cerebrospinal Fluid (Part 3 of 3). Dura mater Arachnoid Arachnoid (periosteal layer) granulation trabecula Cranium CSF fluid Superior movement sagittal sinus Dura mater (meningeal layer) Subdural space Arachnoid mater Cerebral cortex Subarachnoid space Pia mater 5 Fingerlike extensions of the arachnoid membrane, called the arachnoid villi, penetrate the meningeal layer of the dura mater and extend into the superior sagittal sinus. In adults, these extensions form large arachnoid granulations. CSF is absorbed into the venous circulation at the arachnoid granulations. 27  14-2 Brain Protection and Support ▪ Blood supply to the brain – Supplies nutrients and oxygen to brain No energy or oxygen storage – Delivered by internal carotid and vertebral arteries – Most blood is removed from dural venous sinuses by internal jugular veins 28 © 2018 Pearson Education, Inc.  14-2 Brain Protection and Support ▪ Cerebrovascular diseases – Disorders that interfere with/stop blood supply to brain – Cerebrovascular accident (CVA) or stroke Stops blood flow to a portion of the brain – Blood clot or vessel rupture Affected neurons begin to die within minutes 29 © 2018 Pearson Education, Inc.  14-2 Brain Protection and Support ▪ Blood Brain Barrier (BBB) – Isolates CNS tissue from general circulation – Formed by network of tight junctions Between endothelial cells of CNS capillaries – Lipid-soluble compounds can diffuse into the interstitial fluid of CSN O2, CO2, steroids, prostaglandins*, and small alcohols – Astrocytes regulate blood brain barrier by Releasing chemicals that control permeability of endothelium 30 © 2018 Pearson Education, Inc. © 2018 Pearson Education, Inc.  14-2 Brain Protection and Support ▪ Blood-CSF barrier – Formed by specialized ependymal cells surround capillaries of choroid plexus – Limits transfer of compounds to CSF – Allows chemical composition of blood and CSF to differ Examples – Ions, hormones, neurotransmitters, amino acids, proteins, etc. 32 © 2018 Pearson Education, Inc.  14-2 Brain Protection and Support ▪ Four breaks in the BBB* – Portions of hypothalamus secrete hypothalamic hormones (growth hormone, dopamine) – Posterior lobe of pituitary gland Secretes antidiuretic hormone (ADH) and oxytocin – Pineal gland pineal secretions (melatonin, sleep/wake cycles) – Choroid plexus Specialized ependymal cells maintain blood CSF barrier instead 33 © 2018 Pearson Education, Inc.  14-3 The Medulla Oblongata Medulla oblongata ▪ Functions – Controls visceral functions – Coordinates complex autonomic reflexes – Allows brain and spinal cord to communicate ▪ Three groups of nuclei 1. Control autonomic visceral functions/reflexes 2. Sensory and motor nuclei of cranial nerves 3. Relay stations for brain and spinal cord 34 © 2018 Pearson Education, Inc.  14-3 The Medulla Oblongata ▪ (1) Autonomic and reflex nuclei – Reticular Formation Mass of gray and white matter with embedded nuclei Regulates autonomic functions – Ex: blood pressure, breathing, thermoregulation, body position, alertness, and sleep ▪ Two major reflex centers – Cardiovascular centers Cardiac and vasomotor centers Control blood flow through peripheral tissues, heart rate, strength of cardiac contractions – Respiratory rhythmicity centers Set pace for respiratory movements 35 © 2018 Pearson Education, Inc.  14-3 The Medulla Oblongata ▪ (2) Sensory and motor nuclei of cranial nerves – Associated with 5 cranial nerves* Motor commands to neck, pharynx, and back Motor commands to thoracic and peritoneal organs (X) Sensory info from internal ear to vestibule and cochlear (VIII) 36 © 2018 Pearson Education, Inc.  14-3 The Medulla Oblongata ▪ (3) Relay stations along sensory and motor pathways – Gracile nucleus and cuneate nucleus Pass somatic sensory information to thalamus – Solitary nuclei Receive visceral sensory information – Forwards info to other autonomic centers – Olivary complex (Olives) Relay information about somatic motor commands – To cerebellar cortex 37 © 2018 Pearson Education, Inc. Figure 14–6a The Medulla Oblongata. Autonomic Centers Reticular formation (1) Medulla Cardiovascular centers (1) oblongata Solitary nuclei (3) Pons Relay Stations Inferior olive Olivary nucleus (3) Pyramids Cuneate nucleus(3) Decussation of Spinal cord Gracile nucleus (3) pyramids Lateral white columns a Anterior view 38 Figure 14–6b The Medulla Oblongata. Attachments to membranous roof of fourth ventricle Posterior median sulcus Lateral funiculus Posterior funiculi b Posterolateral view 39  14-4 The Pons ▪ Pons components 1. Sensory and motor nuclei of cranial nerves (V, VI, VII, VIII) Jaw muscles, face Vestibular/cochlear 2. Nuclei involved with respiration Apneustic center and pneumotaxic center – Long/deep breaths vs. regulating rate/pattern Modify respiratory rhythm center activity (from medulla) 3. Nuclei and tracts that process and relay information to/ from cerebellum 4. Ascending, descending, and transverse pontine fibers Transverse fibers (axons) connected to tracts – Link nuclei of pons with opposite cerebellar hemisphere 40 © 2018 Pearson Education, Inc. Figure 14–7 The Pons. Pons Cerebellum Fourth ventricle Medulla oblongata Spinal cord Inferior olivary nucleus 41  14-5 The Midbrain Structures of the midbrain ▪ Tectum (roof) – Two pairs of sensory nuclei (corpora quadrigemina) Superior colliculi (visual) – Reflex movements of eyes, head, and neck – Receives info from thalamus Ex. Bright light Inferior colliculi (auditory) – Reflex movements of head, neck, and trunk – Receives info from pons and medulla oblongata Ex. Loud noise 42 © 2018 Pearson Education, Inc.  14-5 The Midbrain Structures of the midbrain ▪ Tegmentum – Red nucleus (many blood vessels) Subconscious motor commands for upper limb positioning and background muscle tone Receives info from cerebellum and cerebrum – Substantia nigra (pigmented gray matter) Releases dopamine – Melanin is byproduct of dopamine synthesis Inhibits Basal Nuclei – Subconsciously controls learned movement and muscle tone 43 © 2018 Pearson Education, Inc.  14-5 The Midbrain Structures of the midbrain ▪ Cerebral peduncles (“little feet”) – Nerve fiber bundles on ventrolateral surfaces – Contain Descending fibers to cerebellum Voluntary motor command fibers ▪ Reticular Activating System (RAS) – Specialized component of reticular formation – Stimulation causes alertness and attentiveness – More in ch. 16 44 © 2018 Pearson Education, Inc. Figure 14–8a The Midbrain. Pineal gland Thalamus a A posterior view. The underlying nuclei are colored only on the right. 45 Figure 14–8c The Midbrain. Tectum ANTERIOR (roof) Superior Cerebellum colliculus Cerebral aqueduct Tegmentum Red nucleus Substantia nigra Cerebral peduncle POSTERIOR c A superior view of a transverse section at the level of the midbrain. 46  14-6 The Cerebellum ▪ Structures of the cerebellum – Cerebellar cortex Gray matter – Folia Folds in cerebellar cortex – Anterior and posterior lobes Separated by primary fissure – Cerebellar hemispheres Separated at midline by vermis 47 © 2018 Pearson Education, Inc.  14-6 The Cerebellum Structures of the cerebellum ▪ Purkinje cell layer (in cerebellar cortex) – Large, branched neuron cell bodies – Each cell receives input from up to 200,000 synapses (most of all neurons in the brain) ▪ Arbor vitae (“tree of life”) – Highly branched, internal white matter of cerebellum – Cerebellar nuclei embedded in arbor vitae Relay information to Purkinje cells – Ex: motor commands for patterned movements 48 © 2018 Pearson Education, Inc.  14-6 The Cerebellum Structures of Cerebellum ▪ Cerebellar peduncles – Tracts that link cerebellum with brainstem, cerebrum, and spinal cord leave the cerebellum as Superior cerebellar peduncles – Links cerebellum with midbrain, diencephalon, and cerebrum Middle cerebellar peduncles – Connected to transverse fibers and cerebellar hemispheres Inferior cerebellar peduncles – Link cerebellum with medulla oblongata – Carry cerebella tracts from spinal cord 49 © 2018 Pearson Education, Inc. Figure 14–9a The Cerebellum (Part 2 of 2). Vermis Anterior lobe Primary fissure Folia Posterior lobe Left Hemisphere Right Hemisphere of Cerebellum of Cerebellum a The posterior, superior surface of the cerebellum, showing major anatomical landmarks and regions 50 Figure 14–9b The Cerebellum (Part 2 of 2). Dendrites Cell body of Purkinje cell Purkinje cells LM × 100 b A sectional view of the cerebellum, showing the arrangement of gray matter and white matter Cerebellum cortex 51 Figure 14–9b The Cerebellum (Part 1 of 2). Anterior lobe Midbrain Choroid plexus Pons of the fourth ventricle Flocculonodular lobe Medulla oblongata Posterior lobe b A sectional view of the cerebellum, showing the arrangement of gray matter and white matter 52  14-6 The Cerebellum ▪ Functions of the cerebellum 1. Adjust postural muscles Balance and equilibrium Automatic adjustments to body positioning 2. Automatic learning and fine-tune conscious and subconscious movements Movements with patterns – Ex: riding bike, playing an instrument Predicts movement (itch face vs. slap face) Autocorrect movements (touch pointer fingers above head) 53 © 2018 Pearson Education, Inc.  14-6 The Cerebellum ▪ Disorders of the cerebellum – Ataxia Disturbance in muscular coordination – Ex: cannot sit or stand without help Caused by – Damage from trauma or stroke – Intoxication (temporary impairment) 54 © 2018 Pearson Education, Inc.  14-7 The Diencephalon ▪ Diencephalon – Integrates sensory information with motor commands – Epithalamus, thalamus, and hypothalamus – Pineal gland In posterior portion of epithalamus Secretes melatonin (ch. 18) 55 © 2018 Pearson Education, Inc.  14-7 The Diencephalon ▪ Thalamus – Filters and relays sensory information From spinal cord and cranial nerves – Not olfactory To cerebral cortex for conscious awareness Not all sensory input reaches our conscious awareness – Relays information between basal nuclei and cerebral cortex 56 © 2018 Pearson Education, Inc.  14-7 The Diencephalon ▪ Thalamus (location) – The third ventricle separates left and right sides – Projection of gray matter Interthalamic adhesion – Extends into third ventricle from each half 57 © 2018 Pearson Education, Inc.  14-7 The Diencephalon ▪ Thalamic nuclei (x 5 groups) – Relay sensory info to basal nuclei and cerebral cortex 1. Anterior nuclei of thalamus Part of limbic system – emotions/basic instincts* 2. Medial nuclei of thalamus Provide awareness of emotional states to frontal lobes 3. Ventral nuclei of thalamus Relay sensory information to cerebral cortex – Touch, pain, pressure, temp., proprioception 58 © 2018 Pearson Education, Inc.  14-7 The Diencephalon ▪ Dorsal nuclei of thalamus 4. Pulvinar nuclei (sensory) 5. Lateral Geniculate bodies Lateral geniculate body (visual- occipital lobes) Medial geniculate body (auditory- limbic and parietal) Integrates sensory information Affects emotional states 59 © 2018 Pearson Education, Inc. Figure 14-10 The Thalamus. Frontal lobe Parietal lobe Occipital lobe a A lateral view of the brain, color coded to indicate the regions that receive input from the thalamic nuclei shown in part (b) Limbic Frontal Parietal lobe Association areas system lobes and cingulate of cerebral cortex gyrus Anterior Medial group group Lateral group Posterior Pulvinar group nucleus Ventral group Auditory input Medial Basal geniculate nuclei nucleus General Lateral Sensory Visual geniculate Cerebellum input input nucleus b An enlarged view of the thalamic nuclei of the left side © 2018 Pearson Education, Inc. Figure 14–10a The Thalamus. Frontal lobe Parietal lobe Occipital lobe a A lateral view of the brain, color coded to indicate the regions that receive input from the thalamic nuclei shown in part b 61 Figure 14–10b The Thalamus. Limbic Frontal Parietal lobe Association areas system lobes and cingulate of cerebral cortex gyrus Medial nuclei Anterior nuclei Lateral nuclei Pulvinar V e n t r a l n u cl e i Auditory input Medial geniculate Basal body nuclei General Lateral sensory Visual geniculate Cerebellum input input body b An enlarged view of the thalamic nuclei of the left side 62 Table 14–2 The Thalamus 63  14-7 The Diencephalon Hypothalamus Structures ▪ Mammillary bodies – Control reflex eating movements – Process olfactory and other sensory information ▪ Infundibulum – A narrow stalk – Connects to pituitary gland ▪ Tuber cinereum (si-nir-E-um) – Between infundibulum and mammillary bodies – Produces hormones that affect pituitary gland 64 © 2018 Pearson Education, Inc. Figure 14–11a The Hypothalamus in Sagittal Section. Parietal lobe Corpus callosum Choroid Septum plexus pellucidum Thalamus (surrounds Fornix third ventricle) Anterior Pineal gland cerebral artery Frontal lobe Hypothalamus Cerebral Anterior aqueduct commissure Cerebellum Optic chiasm Fourth Optic nerve ventricle Infundibulum Tuber Mammillary (cut) cinereum body a The hypothalamus and adjacent portions of the brain 65 Figure 14–11b The Hypothalamus in Sagittal Section. Hypothalamus Nuclei/Centers Nuclei stimulated by: 1. Sensory information from cerebrum, brainstem, and spinal cord. 2. Changes in composition of CSF or interstitial fluid. 3. Chemical stimuli in blood (no BBB). 66  14-7 The Diencephalon ▪ Eight functions of hypothalamus 1. Secretes two hormones ADH (supra-optic nucleus) – reduces water loss by kidneys Oxytocin (paraventricular nucleus) – smooth muscle contractions in uterus, mammary glands (females), and prostate 2. Regulates body temperature Pre-optic area – CNS centers with vasomotor center in medulla 3. Controls autonomic function 4. Coordinates voluntary & autonomic functions 5. Coordinates nervous and endocrine systems inhibit or stimulate endocrine cells; (ex: insulin, growth hormone, testosterone) 67 © 2018 Pearson Education, Inc.  14-7 The Diencephalon 6. Regulates circadian rhythms Suprachiasmatic nucleus 7. Subconscious control of skeletal muscle Motor patterns associated with rage, pleasure, pain, arousal ex: facial expressions, basic motions with sexual activity 8. Produces emotions and behavioral drives Feeding center (hunger) Thirst center (thirst) Satiety center (regulates food intake) Note: conscious sensations and other responses 68 © 2018 Pearson Education, Inc.  14-8 The Limbic System ▪ Limbic system (“Motivational System”) – Functional grouping that Establishes emotional states Links conscious (intellectual) functions of cerebral cortex with autonomic functions of brainstem Facilitates memory storage and retrieval 69 © 2018 Pearson Education, Inc.  14-8 The Limbic System ▪ Components of the limbic system – Limbic lobe of cerebral hemisphere Cingulate gyrus – superior to corpus callosum Dentate gyrus –posterior portion Parahippocampal gyrus – anterior portion Hippocampus (“Sea Horse”) – learning, storage/ retrieval of new long-term memories – Amygdaloid body (amygdala) Acts as interface between the limbic system, cerebrum, and various sensory systems Roles in fight/flight response Roles in fear/anxiety responses Links emotional meanings with memories 70 © 2018 Pearson Education, Inc.  14-8 The Limbic System ▪ Components of the limbic system – Fornix Tract of white matter Connects hippocampus with hypothalamus – Anterior nuclei of thalamus Relay information from mammillary body to cingulate gyrus Experimentally- roles in anger, fear, pain, arousal, pleasure – Reticular formation (brain stem) Stimulation- Alertness, excitement Inhibition - lethargy, sleep 71 © 2018 Pearson Education, Inc. Figure 14–12a The Limbic System. HATCH hippocampus, amygdala, thalamus, cerebrum, hypothalamus Corpus Pineal callosum Fornix gland Cingulate gyrus (superior portion of limbic lobe) Anterior thalamic nuclei Parahippocampal Hypothalamus gyrus (inferior portion of limbic lobe) Mammillary body Hippocampus (within Temporal lobe dentate gyrus, the of cerebrum posterior portion of limbic lobe) a A diagrammatic sagittal section through the cerebrum, showing the cortical areas associated with the limbic system. The parahippocampal gyrus is shown as though transparent to make deeper limbic components visible. 72 Figure 14–12b The Limbic System. Corpus callosum Olfactory tract b A three-dimensional reconstruction of the limbic system, showing the relationships among the major components. 73  14-9 The Cerebrum ▪ Brain activity – Assessed with an electroencephalogram (EEG) Electrodes are placed on brain or skull Electrical activity (brain waves) is observed – Note: constantly changing based on stimulation Used following head trauma or stroke ▪ Types of typical brain waves – Alpha waves – Beta waves – Theta waves – Delta waves 74 © 2018 Pearson Education, Inc. Figure 14–17a Brain Waves. a Alpha waves are characteristic of normal resting adults – Seen in healthy, awake adults at rest with eyes closed 0 Seconds 1 2 3 4 75 Figure 14–17b Brain Waves. b Beta waves typically accompany intense concentration – Higher- frequency waves – Seen in adults who are concentrating or mentally stressed 0 Seconds 1 2 3 4 76 Figure 14–17c Brain Waves. – Seen in children and in intensely frustrated adults – May indicate brain disorder in adults (ex. Tumor) c Theta waves are seen in children and in frustrated adults 0 Seconds 1 2 3 4 77 Figure 14–17d Brain Waves. – Large- amplitude, low- frequency waves – Occur during sleep, in infants, and in awake adults with brain damage d Delta waves occur in deep sleep and in certain pathological 0 Seconds 1 2 3 4 conditions 78  14-9 The Cerebrum ▪ Synchronization of electrical activity between hemispheres – Achieved through a “pacemaker” mechanism – Desynchronization may result from injury or tumor ▪ Seizure* – A temporary cerebral disorder – Accompanied by changes in electrical activity Sudden, uncontrolled – Symptoms depend on region of cortex affected Primary motor cortex- movement Auditory cortex- hear strange sounds Also affects level of consciousness and/or feelings – Two or more episodes within 24 hours is considered epilepsy 79 © 2018 Pearson Education, Inc.  Fundamentals of Anatomy & Physiology Eleventh Edition Chapter 15 Sensory Pathways and the Somatic Nervous System © 2018 Pearson Education, Inc.  Sensory Pathways and Somatic Nervous System Focus for this chapter: ▪ General senses Pathways – Touch, pain, temperature, proprioceptors, pressure, and vibrations ▪ Somatic Nervous System (SNS) motor pathways – Controls contractions of skeletal muscles – Conscious or subconscious 2 © 2018 Pearson Education, Inc.  15-1 Sensory and Motor Pathways ▪ Sensory pathways – Series of neurons that relays sensory information from receptors to CNS for processing using Nerves Tracts Nuclei (sites in cerebral cortex) ▪ Sensory receptors – Monitor specific conditions In the body or external environment – Generates action potentials when stimulated Ex. temperature 3 © 2018 Pearson Education, Inc.  15-1 Sensory and Motor Pathways Reminder of Nervous System Divisions: ▪ Afferent division – Somatic and visceral sensory pathways ▪ Efferent division – Somatic motor pathways Control peripheral effectors SAME- Sensory/Afferent; Motor/Efferent 4 © 2018 Pearson Education, Inc. Figure 15–1 An Overview of Events Occurring Along the Sensory and Motor Pathways. Sensory Pathway Depolarization Arriving of Sensory Action Potential CNS Propagation stimulus Receptor Generation Processing A stimulus produces a If the stimulus depolarizes Axons of sensory neurons Information processing graded change in the the receptor cell to carry information about occurs at every relay membrane potential of threshold, action the type of stimulus synapse. Sensory informa- a receptor cell. potentials develop in the (touch, pressure, tion may be distributed to initial segment. temperature) as action multiple nuclei and centers potentials to the CNS. in the spinal cord and brain. Immediate Involuntary Response Motor Pathway (involuntary) Processing centers in the spinal cord or brainstem may direct an immediate reflex response even before sensations reach the cerebral cortex. Voluntary Response Perception Motor Pathway The voluntary response, which is not (voluntary) Only about 1 percent of immediate, can moderate, enhance, arriving sensations are or supplement the relatively simple relayed to the primary involuntary reflexive response. somatosensory cortex. Note: motor responses can be modified by higher-order functions 5 (learning/memory/planning)  15-2 Sensory Receptors ▪ Sensory receptors – Specialized sensory neurons - or - – Cells monitored by sensory neurons Ex. muscle spindle, tendon organ – ~1% reaches the primary somatosensory cortex ▪ Sensation – Arriving information ▪ Perception – Conscious awareness of a sensation 6 © 2018 Pearson Education, Inc.  15-2 Sensory Receptors ▪ General senses ▪ Special senses – Temperature ▪ Olfaction – Pain ▪ Gustation – Touch ▪ Vision – Pressure Equilibrium – Vibration Hearing – Proprioception (body position) Special Sensory Receptors Located in sense organs (eye or ear) Protected by surrounding tissues 7 © 2018 Pearson Education, Inc.  15-2 Sensory Receptors Detection of stimuli ▪ Transduction – Conversion of an arriving stimulus into an action potential by a sensory receptor ▪ Receptor specificity – Each receptor has a characteristic sensitivity Ex: pressure verses chemical on tongue – May result from structural or accessory cells Ex: Free nerve endings of dendrites – Least specific – Detect chemical, pressure, trauma, temperature related to tissue damage for pain sensation 8 © 2018 Pearson Education, Inc.  15-2 Sensory Receptors Detection of stimuli cont. ▪ Receptive Field – Area monitored by a single receptor cell – The larger the receptive field, the more difficult it is to localize a stimulus Ex. general body field (7 cm) vs fingers (< 1 mm) 9 © 2018 Pearson Education, Inc.  15-2 Sensory Receptors Interpretation of sensory information ▪ Labeled Line – Link between peripheral receptor and cortical neuron – Each carries info about one modality/type of stimulus Ex: touch or light – Perception of stimulus depends on path to CNS Ex: optic nerve – Frequency and pattern of action potentials informs about: Strength, duration, and variation of stimulus 10 © 2018 Pearson Education, Inc.  15-2 Sensory Receptors ▪ Adaptation – Reduction of receptor sensitivity from a constant, painless stimulus Peripheral adaptation – Reduces how much information reaches the CNS Central adaption – Subconsciously restricts amount of info to the cerebral cortex – Conscious and subconscious control Ex. Listening carefully vs. traffic noise; tune out background noise 11 © 2018 Pearson Education, Inc.  15-2 Sensory Receptors Two types of receptors related to adaptation: ▪ Tonic (“slow-adapting”) receptors – Always active – Little peripheral adaptation – Increase/decrease of action potentials directly relate to increase/decrease of stimuli Ex: Pain receptors & proprioceptors ▪ Why do we “want” slow adapting pain and proprioceptors? 12 © 2018 Pearson Education, Inc.  15-2 Sensory Receptors ▪ Phasic (“Fast-adapting”) receptors – Normally inactive – Activate when a constant stimulus stops or changes – Respond strongly at first but then activity decreases Ex. Room temperature, some tactile receptors 13 © 2018 Pearson Education, Inc. Figure 15–3a Tonic and Phasic Sensory Receptors. 14  15-3 General Sensory Receptors ▪ Classifying sensory receptors – Exteroceptors Provide information about external environment – Proprioceptors Report positions of skeletal muscles and joints – Interoceptors Monitor visceral organs and functions 15 © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors ▪ General sensory receptors – Somatic and visceral versions of each type Processing mostly in brainstem or spinal cord – Four types by nature of stimulus 1. Nociceptors 2. Thermoreceptors 3. Mechanoreceptors 4. Chemoreceptors 16 © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors 1. Nociceptors (pain receptors, “noxa” = “harm”) – Free nerve endings with large receptive fields – Tonic/slow receptors – Located in: Superficial portions of skin Joint capsules & within periostea of bones Around walls of blood vessels – May be sensitive to: Temperature extremes Mechanical damage https://www.yourmechanic.com/article/how-to-unfreeze-door-locks Dissolved chemicals released by injured cells – Very painful sensation described as “burning” 17 © 2018 Pearson Education, Inc.  15-3 Classifying Sensory Receptors Two types of axons carry pain sensations: ▪ Myelinated Type A fibers – Carry sensations of fast pain/ prickling pain Ex. injection or a deep cut – Sensations reach the CNS quickly and often trigger somatic reflexes – Relayed to the primary sensory cortex and receive conscious attention ▪ Type C fibers – Carry sensations of slow pain/ burning and aching pain – Cause a generalized activation of the reticular formation and thalamus – You are aware of the pain but only have a general idea of the area affected © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors ▪ Pain Pathway – Sensory neurons release glutamate/ Substance P as neurotransmitters Which facilitate the peripheral neurons May cause pain sensation to be disproportional to injury – Develops in utero ▪ CNS can decrease perception of pain – Thalamus, lower brain stem, reticular formation, and spinal cord – Neuromodulators (endorphins and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6332914/ enkephalins) released by CNS to reduce level of pain sensation 19 © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors 2. Thermoreceptors (temperature receptors) – Free nerve endings located in Dermis Skeletal muscles Liver Hypothalamus – Phasic/fast receptors – 3-4x more cold than heat receptors – Temperature sensations conducted along same pathways that carry pain sensations Sent to reticular formation, thalamus, and (to a lesser extent) the primary somatosensory cortex 20 © 2018 Pearson Education, Inc. https://exetersportspine.com/sleeping-positions-evaluated/  15-3 General Sensory Receptors 3. Mechanoreceptors – Sensitive to physical stimuli that distort plasma membranes – Membranes contain mechanically gated ion channels that open or close in response to Stretching Compression Twisting Other distortions of the membrane 21 © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors ▪ Three classes of mechanoreceptors – Tactile receptors Touch (shape or texture) Pressure (degree of mechanical distortion) Vibration (pulsing pressure) – Baroreceptors Detect pressure changes in blood vessels and in digestive, respiratory, and urinary tracts – Proprioceptors Monitor positions of joints and skeletal muscles 22 © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors ▪ Tactile receptors – Fine touch and pressure receptors Extremely sensitive Narrow receptive fields Provide detailed information about – location, size, shape, texture, direction – Crude touch and pressure receptors Large receptive fields Provide poor localization Give little information about stimulus 23 © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors Six types of tactile receptors in skin 1. Free nerve endings – Sensitive to touch and pressure – Situated between epidermal cells – Tonic/slow receptors – Small receptive fields Ex. Pain and temperature 24 © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors Six types of tactile receptors in skin 2. Root hair plexus nerve endings – Monitor distortions and movements wherever hairs are located – Phasic/fast – Best at detecting initial contact and subsequent movements Ex. clothing 25 © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors Six types of tactile receptors in skin 3. Tactile discs (“Merkel disc”) – Fine-touch and pressure receptors – Sensitive to shape and texture – Extremely sensitive tonic receptors – Very small receptive fields – Mostly found in sites of epidermis that lack hair Ex: Fingertips, lips, external genitalia – Flattened discs contact stratum basale to activate receptor 26 © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors Six types of tactile receptors in skin 4. Bulbous corpuscles (Ruffini corpuscles) – Sensitive to pressure and stretch of skin – Located in reticular dermis – Tonic/slow receptors that show little/no adaptation – Distortion of dermis pulls fibers Ex. sitting on an uncomfortable rock Ex. holding a pen to write 27 © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors Six types of tactile receptors in skin cont. 5. Lamellar Corpuscles (Pacinian corpuscles) – Sensitive to deep pressure Surrounded by concentric layers of collagen Layers separated by interstitial fluid – Fast-adapting/Phasic – Most sensitive to pulsing or high-frequency vibrating stimuli bc fast-adapting – Located in: dermis, deep fasciae joint capsules pancreas, urethra, urinary bladder 28 © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors Six types of tactile receptors in skin cont. 6. Tactile corpuscles (Meissner corpuscles) – Perceive fine touch, pressure, and low-freq. vibration – Adapt within 1 sec; need constant stimulation – Relatively large structures in dermis – Most abundant in eyelids, lips, fingertips, nipples, and external genitalia Ex: forgotten food on lips Clinical significance: ▪ Allow reading in Braille ▪ Fewer in males ▪ Decline with age ▪ Degrade in diabetics/HIV/Parkinson's 29 © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors ▪ Tactile sensations can be affected by: – Infection – Disease – Damage to neuron or sensory pathway ▪ Mapping tactile responses may help with clinical assessments (i.e., Dermatomes) ▪ Related sensations: – Tickling is a light touch; involve psychological factors – Itching*- Histamine (itch) receptors Free nerve endings in skin, eyelids, inner surface of eyelids, and mucous membranes of nose/throat – NOT found in visceral organs Can be worse than pain 30 © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors (back to mechanoreceptor types) ▪ Baroreceptors – Monitor changes in pressure in an organ – Free nerve endings that branch within elastic tissues In walls of distensible organs – Respond immediately to change in pressure but adapt rapidly 31 © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors ▪ Proprioception (still mechanoreceptor) – Somatic sensation only – Monitor: Position of joints Tension on tendons and ligaments State of muscle contractions – Three major groups: Muscle spindles Golgi tendon organs Receptors in joint capsules 32 © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors ▪ Three major groups of proprioceptors – Muscle spindles Monitor skeletal muscle length Trigger stretch reflexes – Golgi tendon organs At junction between skeletal muscle and its tendon Stimulated by tension in tendons Monitor tension during muscle contraction – Receptors in joint capsules Free nerve endings that detect pressure, tension, and movement at the joint ▪ Collectively, integrate information (+ receptors of internal ear) to provide constant, subconscious awareness of body position 33 © 2018 Pearson Education, Inc.  15-3 General Sensory Receptors (back to types of general sensory receptors) 4. Chemoreceptors – Respond to substances dissolved in body fluids* – Exhibit peripheral adaptation in seconds Central adaptation may also occur – No info sent to primary somatosensory cortex – Autonomic control of respiration and cardiovascular activity Carotid bodies – Near origin of internal carotid arteries on each side of neck Aortic bodies – Between major branches of aortic arch Monitor pH, carbon dioxide, and oxygen levels in arterial blood 34 © 2018 Pearson Education, Inc. Figure 15–6 Locations and Functions of Chemoreceptors. Chemoreceptors In and Near Trigger reflexive Respiratory Centers of Medulla adjustments in Oblongata depth and rate of respiration Sensitive to changes in pH and CO2 in cerebrospinal fluid Cranial nerve IX Chemoreceptors of Carotid Bodies Trigger reflexive Sensitive to changes in pH, adjustments in CO2, and O2 in blood respiratory and cardiovascular Cranial nerve X activity Chemoreceptors of Aortic Bodies Sensitive to changes in pH, CO2, and O2 in blood 35  Sensory Pathways Sensory signal can be sent to the CNS via three pathways: First-Order Neuron Sensory neuron delivers sensations directly to the CNS Cell body of a first-order general sensory neuron is in dorsal root ganglion or cranial nerve ganglion Second-Order Neuron Axon of the sensory neuron synapses on an interneuron in the CNS May be located in the spinal cord or brain stem Third-Order Neuron (if present) If the sensation is to reach our awareness, the second-order neuron synapses to a third-order neuron in the thalamus Decussation  15-4 Sensory Pathways ▪ Somatic sensory pathways – Carry sensory information from skin and muscles of body wall, head, neck, and limbs to CNS – Most somatic sensory information Is relayed to the thalamus for processing – Major somatic sensory pathways Spinothalamic pathway Posterior column pathway Spinocerebellar pathway (see note) 37 © 2018 Pearson Education, Inc. Figure 15–7 Sensory Pathways and Ascending Tracts in the Spinal Cord. Posterior Column Pathway Spinal Posterior Gracile fasciculus ganglion root Medulla Oblongata Cuneate fasciculus Spinocerebellar Pathway Posterior spinocerebellar tract Anterior spinocerebellar tract Anterior root Spinothalamic Pathway Lateral spinothalamic tract Anterior spinothalamic tract 38  15-4 Sensory Pathways ▪ Spinothalamic pathway – Sensations of crude touch, pressure, pain, and temp. – First-order neurons enter spinal cord and synapse within posterior horns – Second-order neurons cross to opposite side of spinal cord before ascending – Third-order neurons Synapse in ventral nuclei of thalamus After sorting and processing, sensations are sent to primary somatosensory cortex 39 © 2018 Pearson Education, Inc.  Figure 12.7 Body maps in the primary motor cortex and somatosensory cortex of the cerebrum. Posterior Functional map of the primary sensory cortex and motor cortex Motor Sensory Anterior Motor map in Sensory map in Shoul precentral gyrus postcentral gyrus Head Ha arm Trunk Neck Trunk Elb m Knee Hip Leg Fo w Elb t Arm Wri Hip re Ha Ar der o nd s Fi er ow nd s ng ng er Fi Knee s Th um b um Foot b e Th Nec k Ey Bro se w No e Eye Toes c Fa s Face Genitals Lip Area of sensory/motor cortex devoted to h Lips Teet s particular body region is not proportional Gu m to region’s size, but to number of Jaw Jaw sensory/motor receptors it contains Tongue Primary motor Pharynx Tongue Primary somato- cortex sensory cortex Intra- Swallowing (precentral gyrus) (postcentral gyrus) abdominal © 2018 Pearson Education, Inc. Figure 15-6 Somatic Sensory Pathways (Part 1 of 4). Anterior spinothalamic tracts carry crude touch and pressure sensations. Midbrain Medulla oblongata Anterior spinothalamic tract Spinal cord Crude touch and pressure sensations from right side of body © 2018 Pearson Education, Inc. Figure 15-6 Somatic Sensory Pathways (Part 2 of 4). Lateral spinothalamic tracts carry pain and temperature sensations Midbrain Medulla oblongata Lateral spinothalamic tract Spinal cord Pain and temperature sensations from right side of body © 2018 Pearson Education, Inc.  15-4 Sensory Pathways Abnormality in spinothalamic pathway: ▪ Painful sensations that are not produced where they are perceived to originate: – Phantom limb syndrome continued feeling of pain in amputated limb Sensory neuron or interneuron within spinothalamic pathway is activated – Pathways developmentally programmed – Referred pain Feeling pain in an uninjured part of body when pain originates at another location Visceral pain can manifest as pain in body surface 43 © 2018 Pearson Education, Inc. Figure 15-7 Referred Pain. Referred pain The pain of a Visceral and somatic heart attack is pain fibers travel in frequently felt in Heart same nerves; brain the left arm of males assumes stimulus from common Liver and gallbladder (somatic) region The pain of appendicitis is generally felt first in the area around the navel and then in the right, lower quadrant Stomach Small Ureters carry intestine Ureters urine from Appendix kidneys to Colon bladder. © 2015 Pearson Education, Inc. Table 15-1 Principal Ascending (Sensory) Pathways (Part 1 of 3). © 2015 Pearson Education, Inc.  15-4 Sensory Pathways ▪ Posterior column pathway (dorsal column-medial lemniscus) – Carries sensations of fine touch, vibration, pressure, and proprioception To medulla oblongata – To thalamus To primary sensory cortex – Spinal tracts involved Left and right gracile fasciculus – Inferior half of body Left and right cuneate fasciculus – Superior half of body 46 © 2018 Pearson Education, Inc.  15-4 Sensory Pathways -Posterior Column Pathway ▪ Thalamus processing: – Determines sensation as fine touch, pressure, or vibration ▪ Ability to determine precise location of stimulus – depends on the projection of information from the thalamus to the primary sensory cortex © 2018 Pearson Education, Inc.  Figure 15-6 Somatic Sensory Pathways (Part 3 of 4). Posterior column pathway (i.e., dorsal column-medial lemniscus) Ventral nuclei in thalamus Midbrain Medial lemniscus- decussate into this tract Nucleus gracilis and nucleus cuneatus Medulla oblongata Fasciculus gracilis and fasciculus cuneatus Dorsal root ganglion Spinal cord Fine-touch, vibration, pressure, and proprioception sensations from right side of body © 2018 Pearson Education, Inc. Table 15-1 Principal Ascending (Sensory) Pathways (Part 2 of 3). © 2018 Pearson Education, Inc.  15-4 Sensory Pathways - Spinocerebellar pathway ▪ Spinocerebellar pathway – Cerebellum receives proprioceptor info about Muscles Tendons Joints – This info does not reach our awareness 50 © 2018 Pearson Education, Inc.  Spinocerebellar pathway Figure 15-6 Somatic Sensory Pathways (Part 4 of 4). SPINOCEREBELLAR PATHWAY Posterior spinocerebellar tracts axons do not cross over to the opposite side of the spinal cord. Travel via the inferior cerebellar peduncle of that side. Anterior spinocerebellar tracts PONS Axons cross over twice Once in spinal cord Cerebellum Once in cerebellum Medulla oblongata Sensations travel via superior cerebellar peduncle Spinocerebellar pathway Posterior spinocerebellar tract Anterior spinocerebellar tract Spin al cord Proprioceptive input from Golgi tendon, organs, muscle spindles, and joint capsule receptors © 2018 Pearson Education, Inc. Table 15-1 Principal Ascending (Sensory) Pathways (Part 3 of 3). © 2018 Pearson Education, Inc.  15-4 Sensory Pathways ▪ Visceral sensory pathways – Visceral sensory info is collected by interoceptors Primarily within thoracic and abdominopelvic cavities – Ascends with spinothalamic pathway – Interoceptors include: Nociceptors Baroreceptors Thermoreceptors Tactile receptors Chemoreceptors Not as numerous as in somatic tissues (NO proprioceptors) 53 © 2018 Pearson Education, Inc.  15-4 Sensory Pathways- Visceral sensory pathways ▪ Cranial nerves V, VII, IX, and X – Sensory information from mouth, palate, pharynx, larynx, trachea, esophagus, etc. ▪ Posterior roots of spinal nerves T1-L2 – Receptors located between diaphragm and pelvic cavity ▪ Posterior roots of spinal nerves S2-S4 – Organs in inferior pelvic cavity Large intestines, urethra, base of urinary bladder, prostate gland, cervix of uterus, portions of vagina