Presentation title slide

UNIT B: Human Body Systems Chapter 8: Human Organization Chapter 9: Digestive System Chapter 10: Circulatory System and Lymphatic System Chapter 11: Respiratory System Chapter 12: Nervous System: Section 12.4 Chapter 13: Urinary System Chapter 14: Reproductive System

Chapter 12: Nervous System UNIT B Chapter 12: Nervous System Chapter 12: Nervous System In this chapter, you will learn about the structure and function of the nervous system. How might a researcher study the effects of frequent head trauma? How might one determine which part of the brain has been affected by repeated blunt impacts? Given the available information about CTE, what steps do you feel should be taken to prevent its occurrence (if any)? Sport-Related Head Trauma and Brain Function. Neurosurgeon Dr. Robert Cantu has studied the brains of many deceased athletes, including hockey and football players. He has found that these players often suffered from chronic traumatic encephalopathy (CTE), a degenerative brain disease caused by repeated blunt impact to the head. Chapter opener figure background: Former NHL players Rick Rypien, Wade Belak, and Derek Boogaard had something in common; they were all “enforcers.” They were expected to fight during hockey games. There is another similarity among these men. They are all dead. Each died of causes that increasingly seem tied to their activities on the ice. Neurosurgeon Dr. Robert Cantu has studied the brains of many deceased athletes, including hockey and football players. He has found that these players often suffered from chronic traumatic encephalopathy (CTE), a degenerative brain disease caused by repeated blunt impact to the head. CTE seems to manifest itself in addiction, depression, and anxiety, conditions suffered by some or all of the deceased players. Dr. David Goldbloom, senior medical adviser at Toronto’s Centre for Addiction and Mental Health, thinks it is important not to assume that the deaths of the players were all the result of the same thing. Each was an individual and each had his own mental health history. Rypien and Belak had battled depression, and Boogaard was still recovering from previous concussions. Goldbloom feels that attributing the deaths to CTE is an oversimplification, but he does think further study in this area is worth pursuing. TO PREVIOUS SLIDE

12.4 The Peripheral Nervous System UNIT B Chapter 12: Nervous System Section 12.4 12.4 The Peripheral Nervous System The peripheral nervous system (PNS) contains the motor and sensory pathways. peripheral nervous system (PNS): lies outside the central nervous system and is composed of nerves and ganglia TO PREVIOUS SLIDE

Structure of the PNS UNIT B The PNS is composed of nerves and ganglia. Chapter 12: Nervous System Section 12.4 Structure of the PNS The PNS is composed of nerves and ganglia. Nerves: bundles of axons; the axons in nerves are called nerve fibres Ganglia: swellings associated with nerves that contain collections of cell bodies nerves: fibres bound by connective tissue; found outside the brain and spinal cord nerve fibres: axons that occur in nerves ganglia: (sing., ganglion) swellings associated with nerves that contain collections of cell bodies TO PREVIOUS SLIDE

UNIT B Chapter 12: Nervous System Section 12.4 Cranial nerves Humans have 12 pairs of cranial nerves attached to the brain Nerves can contain sensory input fibres, motor output fibres, or a combination of both Largely concerned with the head, neck, and facial regions Vagus nerve (X) branches to internal organs cranial nerves: nerves that arise from the brain Figure 12.12 Cranial and spinal nerves. a. Ventral surface of the brain showing the attachments of the 12 pairs of cranial nerves. TO PREVIOUS SLIDE

UNIT B Chapter 12: Nervous System Section 12.4 Spinal nerves Humans have 31 pairs of spinal nerves (mix of motor and sensory fibres) Dorsal root: contains sensory fibres that conduct impulses toward the spinal cord Dorsal root ganglion: contains cell bodies of sensory neurons Ventral root: contains motor fibres that conduct impulses away from the spinal cord to effectors Each spinal nerve serves a region of the body in which it is located spinal nerves: nerves that arise from the spinal cord dorsal root ganglia: structures that house the cell body of a sensory neuron Figure 12.12 Cranial and spinal nerves. b. Cross section of the spinal cord showing three pairs of spinal nerves. The human body has 31 pairs of spinal nerves altogether, and each spinal nerve has a dorsal root and a ventral root attached to the spinal cord. TO PREVIOUS SLIDE

UNIT B Chapter 12: Nervous System Section 12.4 Somatic System The PNS is divided into the somatic system and the autonomic system. The somatic system takes sensory information from external sensory receptors to the CNS and motor commands away from the CNS to skeletal muscles Serves the skin, skeletal muscles, and tendons Some actions are due to reflex actions (automatic responses to a stimulus) somatic system: a subdivision of the peripheral nervous system that serves the skin, skeletal muscles, and tendons reflex actions: automatic responses to a stimulus TO PREVIOUS SLIDE

UNIT B Chapter 12: Nervous System Section 12.4 The Reflex Arc A reflex arc is a nerve pathway that carries out a reflex. Reflexes are built-in circuits that allow for protection and survival Reflexes allow the body to react quickly to stimuli that could disrupt homeostasis Reflexes are present at birth and do not require conscious thought Example: withdrawal reflex when touching a sharp object TO PREVIOUS SLIDE

UNIT B Chapter 12: Nervous System Section 12.4 Figure 12.13 A somatic reflex arc showing the path of a spinal reflex. A stimulus (for example, a sharp pin) causes sensory receptors in the skin to generate nerve impulses that travel in sensory axons to the spinal cord. Interneurons integrate data from sensory neurons and then relay signals to motor axons. Motor axons convey nerve impulses from the spinal cord to a sketetal muscle, which contracts. Movement of the hand away from the pin is the response to the stimulus. TO PREVIOUS SLIDE

Autonomic System UNIT B Chapter 12: Nervous System Section 12.4 Autonomic System The autonomic system of the PNS regulates the activity of cardiac and smooth muscle, and glands. autonomic system: part of the peripheral nervous system that regulates the activity of cardiac and smooth muscle, and glands TO PREVIOUS SLIDE

Both divisions function automatically and usually involuntarily UNIT B Chapter 12: Nervous System Section 12.4 The autonomic system is composed of the sympathetic and parasympathetic divisions. Both divisions function automatically and usually involuntarily Innervate all internal organs For each signal, they use two motor neurons that synapse at a ganglion Involved in reflex actions such as blood pressure and breathing rate TO PREVIOUS SLIDE

Sympathetic Division UNIT B Chapter 12: Nervous System Section 12.4 Sympathetic Division The sympathetic division is involved in the “fight or flight” response. Inhibits tears Dilates pupils Inhibits salivation Increases heartbeat Dilates airways Stimulates liver to release glucose Inhibits digestive tract and urination Uses the neurotransmitters epinephrine (adrenaline) and norepinephrine (NE), which act on different cells to add to the “fight or flight” response sympathetic division: division of the autonomic system that is active when an organism is under stress; activates the adrenal medulla to secrete the hormones epinephrine and norepinephrine TO PREVIOUS SLIDE

UNIT B Chapter 12: Nervous System Section 12.4 Figure 12.14 Autonomic system structure and function. Sympathetic preganglionic fibres (left) arise from the cervical, thoracic, and lumbar portions of the spinal cord. Parasympathetic preganglionic fibres (right) arise from the cranial and sacral portions of the spinal cord. Each system innervates the same organs but has contrary effects. TO PREVIOUS SLIDE

Parasympathetic Division UNIT B Chapter 12: Nervous System Section 12.4 Parasympathetic Division The parasympathetic division is involved in the “rest and digest” response. Stimulates tears Constricts pupils Stimulates salivation Decreases heartbeat and blood pressure Constricts airways Stimulates gall bladder to release bile Stimulates digestive tract and urination Uses the neurotransmitter acetylcholine (ACh), which acts on different cells to add to the “rest and digest” response parasympathetic division: division of the autonomic system that is active under normal conditions; uses acetylcholine as a neurotransmitter TO PREVIOUS SLIDE

UNIT B Chapter 12: Nervous System Section 12.4 Figure 12.14 Autonomic system structure and function. Sympathetic preganglionic fibres (left) arise from the cervical, thoracic, and lumbar portions of the spinal cord. Parasympathetic preganglionic fibres (right) arise from the cranial and sacral portions of the spinal cord. Each system innervates the same organs but has contrary effects. TO PREVIOUS SLIDE

UNIT B Chapter 12: Nervous System Section 12.4 TO PREVIOUS SLIDE

Check Your Progress UNIT B Contrast cranial and spinal nerves. Chapter 12: Nervous System Section 12.4 Check Your Progress Contrast cranial and spinal nerves. Explain why, if you touch a hot stove, you usually withdraw your hand before feeling the pain. Summarize the features of the autonomic system that are different from the somatic system. ANSWERS 1. Cranial nerves: Generally associated with sensing and motor control of the head, neck, and facial regions (except the vagus, which controls many organs, tissues, and glands in the neck and body). 12 pairs some contain only sensory fibres, some only motor fibres, and some are mixed nerves with both sensory and motor fibres   Spinal nerves: Generally associated with sensing and motor control in the rest of the body; they are found in the area they serve—e.g., intercostal muscles are innervated by thoracic nerves. 31 pairs contain sensory and motor fibres (mixed nerves) 2. When you touch a hot stove, your hand withdraws before you feel the pain, because the nerve pathway for a reflex arc travels directly through the spinal cord without input from the brain. The pain impulse is travelling up the neck to the brain as the motor impulse is travelling back to the effector muscle. 3. Somatic Type of control: Voluntary Number of neurons per message: one Neurotransmitter: Acetylcholine Effectors: Skeletal muscle Autonomic Type of control: Involuntary Number of neurons per message: two Neurotransmitter: Acetylcholine and norepinephrine Effectors: Smooth and cardiac muscle, glands TO PREVIOUS SLIDE

Check Your Progress UNIT B Chapter 12: Nervous System Section 12.4 Check Your Progress Provide the neurological explanation for the following: You eat a big lunch, then go for a jog, during which your stomach starts to ache. Explain the following: How does the bite of a black widow spider, which injects a powerful AChE inhibitor, cause muscle cramps, salivation, fast heart rate, and high blood pressure? ANSWERS 4. The brain has stimulated your somatic nervous and sympathetic nervous systems more than your parasympathetic. As a result, there is an increase in blood flow to the muscles, heart rate and depth and rate of breathing increase, and digestion is inhibited. There is decreased peristalsis and blood flow to the intestine, which results in discomfort.   5. AChE normally breaks down acetylcholine in the synaptic cleft. The black widow venom is an AChE inhibitor, so acetylcholine in the synaptic cleft is not being broken down. The symptoms of muscle cramps, salivation, fast heart rate, and high blood pressure all are a result of the action of the acetylcholine as a neurotransmitter in the somatic and parasympathetic nervous systems. TO PREVIOUS SLIDE

UNIT B Chapter 12: Nervous System Section 12.4 TO PREVIOUS SLIDE