Sensory and Motor Systems 2024 DRKF PDF

Sensory & Motor Systems THE NERVOUS SYSTEM Year 1- Biology 232 Dr. Rai Khalid FAROOQ Physiology Dept, CMMS [email protected] Sensory Receptors A sensory receptor is a structure that reacts to a physical stimulus in the environment Classification of Sensory Receptors According to Location 1. 2. Extero...

Sensory & Motor Systems THE NERVOUS SYSTEM Year 1- Biology 232 Dr. Rai Khalid FAROOQ Physiology Dept, CMMS [email protected] Sensory Receptors A sensory receptor is a structure that reacts to a physical stimulus in the environment Classification of Sensory Receptors According to Location 1. 2. Exteroreceptors: Detect stimuli from outside the body (Special senses receptors) Interoreceptors: Detect stimuli within the body Directly involved in homeostasis (maintain constant environment) According to Stimulus 1. 2. 3. 4. 5. Mechanoreceptors: detect deformation and stimulated by mechanical forces that cause pressure (Touch, Baroreceptors….) Thermoreceptors detect change in temperature; located in hypothalamus and skin Nociceptors detect tissue damage (pain receptors): Respond to chemicals released by damaged tissues. Photoreceptors detect light energy Chemoreceptors respond to chemical substances in the vicinity (Receptors for taste, smell, blood pH, blood gases Sensation & Perception Sensation is a physical feeling resulting from something that happens to or comes into contact with a receptor in the body, i.e., burning sensation, pain sensation. Or is the input from the physical world obtained by our sensory receptors. Or conscious experience resulting from stimulation of a specific sense organ, sensory nerve, or sensory area in the brain. Perception is the ability to see, hear, or become aware of something through the senses. It is the process by which the brain selects, organizes, and interprets these sensations, like when you perceive and interpret light as color and not sound. It is the physical process during which our sensory organs—those involved with hearing, vision, and taste, for example—respond to these external stimuli and perceive them as sound, images or delicious food. Receptors for different senses stimuli from ↑ physical world Sensation: Obtaining input/stimuli about the physical world by sensory receptors a interpretation of stimuli > when nerve - signals reach cerebellum Perception: Interpretation and awareness of stimuli. Occurs when nerve signals from receptors reach the cerebral cortex in the brain. general e special a Types of Sensation 1. General sensation A Somatic B Visceral 2. Special sensation A Smell, taste, vision etc Components of Sensation occurs in a region that can respond to Stimuli 1. Stimulation: Stimulus occurring in a region of the sensory neuron that can respond to stimuli. 2. Sensory Transduction: Conversion of the stimulus by the receptor into a nerve impulse or action potential. sconvertingStimulSeal N = translation transduction Sensory Transduction All sensory receptors initiate nerve signals. The sensation that results depends on the part of the brain receiving the nerve signals.(i.e., the center in the brain specific for this sensation). Some sensory receptors are free nerve endings or encapsulated nerve endings and others are specialized cells closely associated with neurons. Sensory transduction is mediated by opening or closing of specific ionic channels. Sensory Transduction -sensory Plasma membranes of sensory receptors contain receptor proteins that react to the stimulus. Binding of stimulus causes ion channels to open with flow of ions across the membrane. 3 4. I. 2. receptors' Plasma Proteins have receptor proteins that react to stimulus - binding of stimulus causes lon channels to open. Somatic Sensory Pathways “soma" means body Somatic Senses detect touch, pain pressure, temperature, and tension on the skin and in internal organs. receptors generate nerve Receptors generate nerve signals that pass through sensory fibers to the spinal cord and up ascending tracts to the brain. The thalamus is an important relay station for all sensory input (Except Smell). Ascending sensory tracts cross over in the spinal cord and medulla (brainstem). Therefore sensation from one half of the body travels to the opposite cerebral hemisphere. pass through signals sensory fibers ↓ to spinal cords Y brain thalamus important Sensory inputs ascending for sensory cross over Spinal cord and medulla sensation from travel to all except smell right left side side The Cerebrum Largest portion of the brain 2 hemispheres Each hemisphere divided into 4 lobes. = See Frontal lobe: Primary motor area and conscious thought Temporal lobe: Primary auditory, smell and speech area Parietal lobe: Primary somatosensory and taste area Occipital lobe – Primary visual area Cerebral Cortex: A thin, highly convoluted outer layer of grey matter that covers the cerebral hemispheres. Gyri and sulci create the folded appearance of the brain. Y cerebellum : largest portion of the brain cerebellum temporal frontal Primary auditory primary motor consious Cerebral cortex : thin outer 3, Sukci gyul : thought smell Parletal Primary somatosensory 3 speech taste layer covers cerebral hemispheres create folded appearance of brain Primary Somatosensory info from Skin sensory recieves Skeletal muscles Primary motor cortex m motor function located in frontal lobe generates : signals neural from Premotor : impulses, m1 cross lles in voluntary commands to skeletal body midline to other side front of primary motor trunk muscles controls proximal supplementory : Iles above premotor involved in Planning corticospinal tract : decusation : fibers complex movement only direct in way from brainstem crosses opposite side of body. Broca's area in - - left inferior frontal gyrus production of speech Wernicke's - - - language area left posterior superior temporal gyrus comprehension damage cortex to Spinal Lord carsed by stroke or brain injury muscles occipital Visual Sensory Areas of the Brain Primary Somatosensory Area Receives sensory information from the skin and skeletal muscles. Each part of the body is represented, with larger allocation for body areas with acute sensation. (Cortical Body Map or HOMUNCULUS). Somatosensory Somatosensory Association Area Processes, analyses and integrates sensory information from the skin and muscles. Primary Areas for Special Senses Association Areas for Special senses - - Skin Skeletal muscle The Motor System- Motor Regions of the Brain Primary Motor Cortex (M1) One of the principal brain areas involved in motor function. M1 is located in the frontal lobe of the brain. Generates neural impulses or voluntary commands to skeletal muscles. Signals from M1 cross the body’s midline to activate skeletal muscles on the opposite side of the body. Stroke on one side of the brain causes weakness or paralysis of muscles on the other side of the body. Every part of the body is represented in the primary motor cortex. Amount of brain matter allocated to a body part depends on the complexity of movement. Hand movements require accuracy Speech and facial movements. The Motor System- Motor Regions of the Brain Signals from M1 cross the body’s midline to activate skeletal muscles on the opposite side of the body, meaning that the left hemisphere of the brain controls the right side of the body, and the right hemisphere controls the left side of the body. A lot of cortical space is required to control the complex movements of the hand and fingers, and these body parts have larger representations in M1 than the trunk or legs, whose muscle patterns are relatively simple Secondary Motor Cortices Other regions of the cortex involved in motor function Premotor Area: Lies just in front of the primary motor cortex. It controls the more proximal muscles and trunk muscles of the body. Supplementary Motor Area Lies above, or medial to, the premotor area, also in front of the primary motor cortex. It is involved in the planning of complex movements and in coordinating two-handed movements. The supplementary motor area and the premotor regions both send information to the primary motor cortex. Descending Motor Pathways The descending tracts are the pathways by which motor signals are sent from the brain to lower motor neurones in the spinal cord that control skeletal muscles. Neurons in M1, supplementary motor area (SMA) and premotor cortex give rise to the fibers of the corticospinal tract. The corticospinal tract is the only direct pathway from the cortex to the spinal cord. In the brainstem most fibers cross over to the opposite side of the body : (Decussation). Broca’s and Wernicke’s Areas – Speech and Language Broca’s area is found in the left inferior frontal gyrus. It is specialized for production of human speech & language. Damage to Broca’s area is expressive (or non-fluent) Broca’s aphasia, i.e., speech impairment (unable to speak). Wernicke’s area is located in the left posterior superior temporal gyrus. It is responsible for comprehension of written and spoken language. An individual with damage to Wernicke’s area can speak fluently, but his speech is often nonsensical and lacks meaning (fluent aphasia or Wernicke’s aphasia) and unable to understand language. Damage is caused by stroke or brain injury Basal Nuclei (Ganglia) Subcortical Structures Masses of grey matter deep within the brain (Subcortical). Influence and regulate muscle movements. Ensure that proper muscle groups are stimulated or inhibited. Inhibit unnecessary movements. Parkinson’s disease A progressive nervous system disorder that affects movement. Degeneration of specific neurons in basal nuclei. Symptoms include: shaking (Tremor), rigidity, slowness of movement, and difficulty with walking. Cerebellum Lies under occipital lobe of the cerebrum. Made of two hemispheres. Receives sensory information from the eyes, ears, joints and muscles about the position of body parts. Cerebellum sends signals to skeletal muscles by way of the brainstem. Maintains posture and balance. Ensures smooth, coordinated voluntary movements. Involved in learning of new motor skills. Damage to the cerebellum does not cause paralysis but might lead to a lack of balance, slower movements, and tremors (shaking).