Higher Human Biology Unit 3 – Neurobiology and Immunology Section 17 – Division of the Nervous System and Neural Pathways

What Can You Remember? What is the CNS made up of? What are the 3 main parts of the brain? What is a reflex action? What makes up the reflex arc? What is a synapse? Brain and Spinal cord Medulla Cerebrum Cerebellum Sensory, Inter and Motor Neuron Where two neurones meet, there is a tiny gap that a signal must cross

a – Structure of the Central Nervous System (CNS) and the Peripheral Nervous System (PNS) We will be learning… To describe the structure of the central nervous system To describe the structure of the peripheral nervous system To describe the structures of the somatic nervous system To explain the pathway of impulses through sensory and motor neurones. To state the function of the autonomic nervous system (ANS) To describe the antagonistic actions of the sympathetic and parasympathetic systems on heart rate, breathing rate, peristalsis and intestinal secretions.

The Nervous System The nervous system can be divided into Central Nervous System (CNS) this is made of the brain and spinal cord. This also includes the retina and optic nerve. the Peripheral Nervous System (PNS) this is made up of all other neurons throughout the rest of the body.

The Nervous System Overview Central Nervous System (CNS) Brain Spinal cord Peripheral Nervous System (PNS) Autonomic Nervous System (ANS) Sympathetic Parasympathetic Somatic Nervous System (SNS) The Nervous System Overview

What is the Central Nervous System? The nervous system of the human body is responsible for numerous functions, such as: Analysing sensory information from the body and external environment e.g. sight, sound, touch etc. 2. Storing some information 3. Making decisions regarding appropriate responses and behaviours. It produces motor responses by causing muscular contractions or secretion from glands.

The Central Nervous System Information from the sensory nerves is sorted out by the CNS. Information from the CNS is then carried by the motor nerves to the appropriate muscles which then contract.

The Peripheral Nervous System (PNS) The PNS is comprised of sensory and motor neuron pathways which pass information to and from the CNS via electrical impulses. When a stimulus is detected by receptors in external sensory organs (e.g. eyes, ears etc) or internally (e.g. thermoreceptors in the hypothalamus), an impulse is carried along sensory nerve cells (neurons) to the CNS. This keeps the brain in touch with what is going on in the body's external and internal environments. The CNS processes the information and impulses are transmitted along motor neurons to effectors, such as muscles and endocrine glands, which bring about a response, such as muscle contraction or hormone/enzyme secretion.

The Peripheral Nervous System (PNS) Nerve impulses carried by sensory neurons Nerve impulses carried by motor neurones CNS external e.g. skin internal e.g. thermoreceptors Receptors e.g. muscles Effectors response stimuli e.g. temperature of blood/skin e.g. muscular contraction

The Peripheral Nervous System (PNS) Somatic Nervous System SNS Autonomic Nervous System (ANS). This tends to control our basic activities, the ones that do not tend to require conscious thought e.g. heart rate, breathing, peristalsis, etc. The autonomic nervous system also controls endocrine glands which regulate growth and the activities of other tissues. These include the pituitary, thyroid, pancreas and adrenal glands. This controls the skeletal muscles through the action of sensory and motor neurons and is involved in mostly voluntary actions, such as walking and speaking. The SNS is also responsible for involuntary reflex actions e.g. limb withdrawal.

Somatic Nervous System SNS contains sensory and motor neurons which control the voluntary movement of skeletal muscles SNS brings about some involuntary actions (e.g. reflex response) but majority of actions are under voluntary control (e.g. picking 4 favourite chocolates out a large box of chocolates)

The Autonomic Nervous System (ANS) The autonomic nervous system (ANS) is responsible for regulating internal structures such as the heart, blood vessels, bronchioles and alimentary canal. This regulation occurs through automatic, involuntary actions which involve sensory and motor neurones. The autonomic nervous system is involved in homeostatic control (e.g. regulation of body temperature or osmoregulation). The nerves of the ANS arise in the brain and emerge from the spinal cord at numerous points to reach the organs that they stimulate. The ANS is made up of two parts, the sympathetic and the parasympathetic systems.

The Peripheral Nervous System (PNS)

Agonist/Antagonist on Sympathetic Nervous Control The sympathetic and parasympathetic systems of the ANS are antagonistic, meaning that they affect many of the same structures but in opposite ways in order to maintain a stable internal environment The sympathetic system is involved in the ‘fight or flight’ response, whilst the parasympathetic system is involved in the ‘rest and digest’ response. The former prepares the body for action and the latter returns the organism to an energy-conserving state.  As these systems work on the same structures but have opposite effects, they are said to have an antagonistic relationship.

Sympathetic Nerve Control – “Fight or Flight“ Is in control when the body is active or excited; this raises activity levels It acts on heart to increase heart rate It increases breathing rate It increases blood flow to muscles It decreases blood flow to digestive system (slows digestion) It increases perspiration (i.e. sweating) https://www.youtube.com/watch?v=mtRrxNTnyh8

Parasympathetic Nerve Control – “Rest and Digest” Is in control in times of rest and relaxation; slows functions and conserves resources It acts on heart to lower heart rate It slows breathing rate It decreases blood flow to muscles It increases blood flow to digestive system (increases digestion)

Parasympathetic System   Sympathetic System Parasympathetic System Type of response “fight or flight” “rest and digest” Response occurs At start of event when sensory nerves stimulated At end of event when excitement is over Heart Rate The rate and force of contraction of cardiac muscle increases. Which results in more blood to muscles and less at the gut and skin. Rate and force of contraction of cardiac muscle decreases. This results in less blood to the muscles, normal levels restored. Peristalsis increases Blood Pressure Increases Return to normal Breathing Rate Muscles in bronchioles become relaxed. Rate of contraction of diaphragm and intercostal muscles increases. This results in increased gas exchange. Muscles in bronchioles become contracted. Rate of contraction of diaphragm and intercostal muscles decreases. This results in reduced gas exchange. Nervous perspiration Increases - Thudding heart White face with fear Clammy armpits and hands Digestion Rate of contraction of smooth muscle in wall of digestive tract decreases. Rate of blood flow to digestive tract decreases.  Result: reduced digestion Rate of contraction of smooth muscle in wall of digestive tract increases. Rate of blood flow to digestive tract increases. Result: normal digestion. Adrenaline (epinephrine) Produced - Fight or run away! Not produced - Return to normal to help body conserve resources and store energy

b – Structure and Function of Converging, Diverging and Reverberating Neural Pathways We will be learning… To explain the structure and function of converging neural pathways To describe the transfer of impulses through a converging neural pathway To explain the structure and function of diverging neural pathways To describe the transfer of impulses through a diverging neural pathways To explain the structure and function of reverberating neural pathways To describe the transfer of impulses through a reverberating neural pathways

Converging Neural Pathways Impulses from several neurons travel to one neuron (concentrating impulses) Example: Rods & Cones in eye This increases the sensitivity to excitatory or inhibitory signals https://www.youtube.com/watch?v=yzyphSTkW2U https://www.youtube.com/watch?v=TF_T3d92gZ4

Nerve Impulses through Converging Neural Pathways Light enters the eye through the transparent cornea, passes through the aqueous humour, the lens, and the vitreous humour, where it finally forms an image on the retina. When these photoreceptors are stimulated by light, they produce electrical signals that are transmitted to the brain via the optic nerve. The optic nerves from the two eyes join inside the brain. The brain uses information from each optic nerve to combine the vision from the two eyes allowing you to see one image. https://www.youtube.com/watch?v=2PD55fyRBxI

Can You Find your Blind Spot? Auto-fill The optic nerve—a bundle of nerve fibres that carries messages from your eye to your brain—passes through one spot on the light-sensitive lining, or retina, of your eye. In this spot, your eye’s retina has no light receptors. When you hold the card so the light from the dot falls on this spot, you cannot see the dot. Now try the blind spot activities

Diverging Neural Pathways Impulses from one neuron travel to several neurons affecting more than one destination at the same time Example: Temperature control – muscles, arterioles, sweat glands)

Nerve impulses through diverging neural pathways Diverging neural pathways carry impulses from the hypothalamus to effector cells in the skin (hair erector muscles), sweat glands and skin arterioles. The hypothalamus is therefore able to exert a co-ordinated control over the structure involved in temperature control such as:

Reverberating Neural Pathways Neurons later in the pathway link with earlier neurons sending the impulse back through the pathway (this allows repeated stimulation) Example: breathing

Nerve impulses through reverberating neural pathways The respiratory centres that control your rate of breathing are in the brainstem or medulla. The nerve cells that live within these centres automatically send signals to the diaphragm and intercostal muscles to contract and relax at regular intervals.

a – Structure of the Central Nervous System (CNS) and the Peripheral Nervous System (PNS) Now I can….. Describe the structure of the central nervous system Describe the structure of the peripheral nervous system Describe the structures of the somatic nervous system Explain the pathway of impulses through sensory and motor neurones. State the function of the autonomic nervous system (ANS) Describe the antagonistic actions of the sympathetic and parasympathetic systems on heart rate, breathing rate, peristalsis and intestinal secretions.

b – Structure and Function of Converging, Diverging and Reverberating Neural Pathways Now I can….. Explain the structure and function of converging neural pathways Describe the transfer of impulses through a converging neural pathway Explain the structure and function of diverging neural pathways Describe the transfer of impulses through a diverging neural pathways Explain the structure and function of reverberating neural pathways Describe the transfer of impulses through a reverberating neural pathways

Word Definition Central nervous system (CNS) brain and spinal cord Peripheral nervous system (PNS) all peripheral nerves Cerebellum area of the brain that contains the balance and coordination centres Cerebral cortex cells of the cerebrum Cerebrum region of the brain that has motor, sensory and association areas Parasympathetic nervous system fibres of the autonomic nervous system that prepare body systems for rest Sympathetic nervous system fibres of autonomic nervous system that prepare bosy systems for action Somatic nervous system (SNS) controls the voluntary action of the skeletal muscle

Questions Name the structures of the central nervous system Describe the functions of the central nervous system Describe the structures of the peripheral nervous system (PNS). Describe the differences in structure between the autonomic (ANS) and somatic nervous systems (SNS) Brain and spinal cord The CNS processes the information sent from the senses along sensory neurons and will send out impulses along motor neurons to effectors. The PNS is comprised of sensory and motor neuron pathways SNS involves the action of sensory and motor neurons while the nerves of the ANS arise in the brain and emerge from the spinal cord at numerous points to reach the organs that they stimulate.

More Questions! 5. Describe the functions of the peripheral nervous system (PNS). 6. Describe the differences in function between the autonomic (ANS) and somatic nervous systems (SNS) PNS pass information to and from the CNS via electrical impulses. SNS is involved in mostly voluntary actions, such as walking and speaking. The SNS is also responsible for involuntary reflex actions. ANS is responsible for regulating internal structures such as the heart, blood vessels etc.

7. Describe the functions of the sympathetic and parasympathetic system. 8. Describe the antagonistic nature of the sympathetic and parasympathetic system. Parasympathetic system is in control in times of rest and relaxation; slows functions and conserves resources. The sympathetic system is in control when the body is active or excited; raises activity levels They work on the same structures but have opposite effects

Give an account of the divisions of the nervous system. (5 marks) The nervous system is divided into the central nervous system and the peripheral nervous system. The central nervous system consists of the brain and spinal cord. The peripheral nervous system comprises all the sensory and motor neurons which connect it to the rest of the body. The peripheral nervous system is sub-divided into the somatic and the autonomic nervous systems. The somatic nervous system controls the voluntary activity of the skeletal muscles (and thus all movement) via its sensory and motor neurons. The autonomic nervous system is further divided into the sympathetic and the parasympathetic nervous systems, which act antagonistically.