The Nervous System and Special Senses PDF

Chapter 7 The Nervous System and Special Senses Fundamentals of Anatomy and Physiology  The Nervous System Control center and communication network Directs functions of body’s organs and systems Interprets external environment Determines reaction to change...

Chapter 7 The Nervous System and Special Senses Fundamentals of Anatomy and Physiology  The Nervous System Control center and communication network Directs functions of body’s organs and systems Interprets external environment Determines reaction to change  The Nervous System Homeostasis: balanced internal environment Controlled by nervous and endocrine systems  Organization Central Nervous System (CNS): brain and spinal cord Peripheral Nervous System (PNS) Afferent peripheral system ▪ Sensory neurons Efferent peripheral system ▪ Somatic ▪ Autonomic: sympathetic and parasympathetic.. “Fight or Flight” “Rest and Digest” Classification of Nerve Cells  Neuroglial Cells (Glial cells) Astrocytes: support, connection, blood-brain barrier Oligodendroglia: support, myelin sheath formation (CNS) Microglial: phagocytosis Ependymal: line the ventricles of the brain Schwann: myelin sheaths in the peripheral nervous system see Figure 10-2 on page 236.  The Structure of a Neuron Cell body - nucleus and metabolic center of the cell Dendrites: receptive areas Axon: extension of cell body ▪ Schwann cells - produce myelin sheaths in jelly-roll like fashion ▪ Nodes of Ranvier - gaps in myelin sheath along the axon. The Structure of a Neuron  The Structure of a Neuron Multipolar: several dendrites coming off cell body ▪ Brain and Spinal Cord Bipolar: one dendrite and one axon ▪ Special Sense Organs (eyes, ears, nose) Unipolar: one process extending from cell body ▪ Most sensory neurons.  Classification of Neurons Receptors: detect environmental stimuli Sensory: receive impulse from receptor site (unipolar) Interneuron: transmit impulse for interpretation and processing (multipolar) Motor: reaction to the stimulus (multipolar) The Reflex Arc  The Reflex Arc The pathway that results in a reflex. Simplest pathway able to receive a stimulus, enter the CNS(spinal cord) for immediate interpretation, and produce a response.  The Reflex Arc Involuntary reaction to external stimulus  The Reflex Arc Knee-jerk reflex Maintain homeostasis Heartbeat, breathing rates, and digestion Coughing (choke reflex) Sneezing Swallowing Vomiting Grouping of Neural Tissue  Grouping of Neural Tissue White matter ▪ Groups of myelinated axons ▪ Forms nerve tracts in CNS Gray matter ▪ Nerve cell bodies and dendrites ▪ Unmyelinated axon bundles ▪ Cortex: gray matter on surface of brain  Grouping of Neural Tissue Nerve: bundle of fibers outside CNS Ganglia: nerve cell bodies outside CNS Tract: bundle of fibers inside CNS Nucleus: nerve cell bodies and dendrites inside CNS Horns: areas of gray matter in spinal cord The Spinal Cord  The Spinal Cord Continuation of medulla oblongata 31 segments each with a pair of spinal nerves Protected by meninges ▪ Dura mater ▪ Arachnoid ▪ Pia mater.  Functions of the Spinal Cord Conveys sensory impulses to the brain Integrates reflexes Spinal nerves connect at roots Dorsal root: sensory Ventral root: motor The Spinal Nerves  The Spinal Nerves All 31 pairs arise from union of dorsal and ventral roots Mixed nerves consisting of motor and sensory fibers Most exit vertebral column between vertebrae  The Spinal Nerves Named and numbered according to region and level of spinal cord. ▪ Cervical: 8 pairs ▪ Thoracic: 12 pairs ▪ Lumbar: 5 pairs ▪ Sacral: 5 pairs ▪ Coccygeal: 1 pair The Brain  The Brain Brain is divided into four main parts: ▪ Brainstem: controls breathing, heartbeat rates and reactions to auditory and visual stimuli ▪ Diencephalon: controls homeostasis ▪ Cerebrum: controls intellectual processes and emotions ▪ Cerebellum: maintains body posture and balance The Principal Parts of the Brain  The Principal Parts of the Brain Protection Cranial bones Meninges Cerebrospinal fluid (CSF) Ventricles Interventricular foramen  The Principal Parts of the Brain. The Anatomy and Functions of the Brainstem  The Anatomy and Functions of the Brainstem The brainstem consists of the medulla oblongata, the pons varolii, and the midbrain. It connects the brain to the spinal cord. It is a very delicate area of the brain because damage to even small areas could result in death.  The Anatomy and Functions of the Brainstem Medulla oblongata ▪ Ascending and descending tracts ▪ Connect spinal cord with the brain ▪ Some tracts cross over in medulla ▪ Reticular formation: controls consciousness and arousal ▪ Reflex centers  The Anatomy and Functions of the Brainstem Pons varolii ▪ Connects spinal cord with brain ▪ Connects parts of brain with each other ▪ Helps control breathing  The Anatomy and Functions of the Brainstem Midbrain (Mesencephalon) ▪ Ventral cerebral peduncles: convey impulses from cortex to pons and spinal cord ▪ Dorsal tectum: Reflex center Controls movement of head and eyeball (visual stimuli) Controls movement of head and trunk (auditory stimuli) The Anatomy and Functions of the Diencephalon  The Anatomy and Functions of the Diencephalon The diencephalon is superior to the midbrain and between the two cerebral hemispheres Optic tracts – optic nerves Mamillary bodies: memory and emotional responses Thalamus ▪ Relay station for sensory impulses ▪ Interpretation center for pain, temperature, and touch Epithalamus ▪ Contains pineal gland  The Anatomy and Functions of the Diencephalon Hypothalamus: homeostasis ▪ Controls and integrates autonomic nervous system ▪ Receives sensory impulses from internal organs ▪ Controls pituitary gland and links endocrine and nervous systems  The Cerebrum: Structure and Function  The Cerebrum: Structure and Function.  The Cerebrum: Structure and Function The cerebrum makes up the bulk of the brain. Cerebral cortex: gray matter surface Longitudinal fissure separates two hemispheres Gyri: folds Sulci: grooves Corpus callosum: bridge connecting two hemispheres  The Cerebrum: Structure and Function Surface of the cortex ▪ Motor areas control muscular movements ▪ Sensory areas interpret sensory impulses ▪ Association areas process emotions and intellect  The Cerebrum: Structure and Function Cerebral hemispheres ▪ Frontal lobe: muscle movement, moods, aggression, smell, motivation ▪ Parietal lobe: touch, pain, balance, taste, temperature ▪ Temporal lobe: hearing, smell, memory, abstract thought, judgment ▪ Occipital lobe: vision  The Cerebrum: Structure and Function. Areas of Brain Function  The Cerebellum: Structure and Function  The Cerebellum: Structure and Function The cerebellum is the second largest portion of the brain. Butterfly-shaped Two partially separated hemispheres connected by vermis Functions: ▪ Coordinating muscular movements ▪ Maintaining posture ▪ Maintaining balance The Autonomic Nervous System  The Autonomic Nervous System Subdivision of efferent PNS Functions without conscious effort Regulates functions of internal organs Assists in maintaining homeostasis Helps deal with emergency situations  The Autonomic Nervous System Sympathetic ▪ Energy and stressful situations ▪ Increases heartbeat and breathing rates ▪ Neurotransmitters: acetylcholine and norepinephrine The sympathetic division prepares us for physical activity by increasing blood pressure and heartbeat rate, it dilates respiratory passageways for increased breathing rates, and it stimulates sweating. It also causes the release of glucose from the liver as a quick source of energy while inhibiting digestive activities.  The Autonomic Nervous System Parasympathetic ▪ Restores body to nonstressful state ▪ Neurotransmitter: acetylcholine ▪ Stimulates digestion, urination, and defecation The parasympathetic division stimulates digestion, urination, and defecation. It also counteracts the effects of the sympathetic division by slowing down heartbeat rate, lowering blood pressure, and slowing the breathing rate. It is also responsible for the constriction of the pupil of the eye.. The Special Senses  The Sense of Smell Molecules in air dissolve in nasal mucus Bipolar sensory neurons transfer chemical impulse Olfactory bulbs receive impulse Impulse sent to olfactory cortex Odor variety dependent on brain interpretation  The Sense of Smell.  The Sense of Taste Taste buds on tongue, palate, and pharynx Taste bud cell types ▪ Exterior capsule: epithelial cells ▪ Interior: taste cells Taste depends on chemicals dissolved in saliva Taste influenced by olfactory sensations  The Sense of Taste. C. Sweet D. Sour E. Salty F. Bitter  The Sense of Sight Eyes protected by eyelids and eyelashes Tears ▪ Lubricate the eyes ▪ Contain bacteriolytic lysozyme enzyme ▪ Contain salt and gamma globulin  The Sense of Sight.  The Sense of Hearing and Equilibrium Outer ear ▪ Auricle: external, visible, flexible part ▪ External auditory meatus ▪ Lined with hair and ceruminous glands ▪ Tympanic membrane: vibrates in response to sound  The Sense of Hearing and Equilibrium.  The Sense of Hearing and Equilibrium Middle ear ▪ Auditory ossicles: malleus, incus, and stapes ▪ Openings: oval and round windows ▪ Eustachian tube: equalizes pressure Inner ear ▪ Cochlea: hearing  The Sense of Hearing and Equilibrium.  Thank You! Do you have any questions for me before we go?