6.5 Nervous System

What is the nervous system? A network of specialized cells that communicate information about an animal's surroundings and itself Nervous system processes this information and causes reactions in other parts of the body Specialized cells called neurons

What are the two main sections of the nervous system? Central Nervous System— Brain and spinal cord Peripheral Nervous System— Composed of nerves that branch from the CNS and connect the CNS to the rest of the body

The CNS receives impulses from the nerves of the PNS How do the CNS and PNS work together to transmit signals and responses? The CNS receives impulses from the nerves of the PNS CNS interprets impulses Transmits the corresponding signals back to the origin through the PNS Thus controlling the functions of the entire body

Along what route are nerve impulses relayed to and from the CNS? Nerve impulses are conducted from receptors to the CNS by sensory neurons within the CNS by relay neurons from the CNS to effectors (muscles) by motor neurons

Be able to draw this motor neuron. Cell body Nucleus Dendrite Axon Myelin sheath Node of Ranvier Axon terminals / synaptic knobs

Identify the components of this motor neuron. Cell body Nucleus Dendrite Axon Myelin sheath Node of Ranvier Axon terminals / synaptic knobs

Resting Potential and Action Potential the membrane potential of a neuron membrane when not conducting an impulse What is the resting potential of a resting neuron? a resting neuron has a resting potential of about -70 millivolts Action potential— is the state of the cell membrane while conducting an impulse

Impulse Transmission In resting neurons, there exists an imbalance of ions inside and outside of the cell membranes. The cytoplasm just inside the membrane is negative in charge, and the fluid just outside the membrane is positive. The membrane is said to be polarized. Like a flashlight battery, the difference in electrical charge carries potential energy, which can be measured as a voltage An action potential is triggered when a nerve impulse triggers voltage-gated sodium channels to open, and sodium ions rush into the cell, reversing the charges Now the cytoplasm just inside the membrane becomes positive in charge, and the fluid just outside the membrane becomes negative. Very quickly, the sodium channels close, while voltage-gated potassium channels open, allowing potassium ions to rapidly diffuse out. The plasma membrane returns to being positive on the outside and negative on the inside, and the potassium channels close

Action Potential and Impulse Transmission Diagram

Synaptic Transmission nerve impulse travels to end of the neuron this causes synaptic vesicles to fuse with membrane the vesicles release neurotransmitter molecules into synaptic cleft these neurotransmitter molecules bind to receptors on next neuron this causes ion channels to open on that neuron sodium ions rush in, changing the polarity of the membrane, and an action potential is triggered in the receiving cell

Synaptic Transmission Diagram

1. Outline the general organization of the human nervous system. IB Exam Question 1. Outline the general organization of the human nervous system. The nervous system is divided into two main parts: the central nervous system (CNS), and the peripheral nervous system (PNS) The organs of the CNS are the brain and the spinal cord The PNS is composed of nerves that branch from the CNS and connect the CNS to the rest of the body The CNS receives impulses from the nerves of the PNS and interprets them, and transmits the corresponding signals back to the origin through the PNS, thus controlling the functions of the entire body Both the CNS and PNS is composed of specialized cells called neurons that carry rapid electrical impulses

Drawing must contain nucleus; cell body; axon; dendrites; IB Exam Question 2. Draw a labelled diagram to show the structure of a motor neuron and indicate with an arrow the direction of the nerve impulse. Drawing must contain nucleus; cell body; axon; dendrites; myelin sheath; node of Ranvier; synaptic knob;

3. Define resting potential and action potential. (2 marks) IB Exam Question 3. Define resting potential and action potential. (2 marks) Resting potential is the membrane potential of a neuron membrane when not conducting an impulse. Action potential is the state of the cell membrane while conducting an impulse

A. Voltage-gated sodium ion channels open and Na+ is pumped in. IB Exam Question 4. In a nerve impulse, what happens at the site following the highest point of the action potential? (1 mark) A. Voltage-gated sodium ion channels open and Na+ is pumped in. B. Voltage-gated sodium ion channels open and Na+ diffuses out. C. Voltage-gated potassium ion channels open and K+ is pumped out. D. Voltage-gated potassium ion channels open and K+ diffuses out. Correct answer: D

5. Explain how a nerve impulse passes along a non-myelinated neuron (axon). IB Exam Question In resting neurons, there exists an imbalance of ions inside and outside of the cell membranes. This is called the “resting potential” and represents potential energy! The cytoplasm just inside the membrane is negative in charge, and the fluid just outside the membrane is positive. The membrane is said to be polarized. Like a flashlight battery, the difference in electrical charge carries potential energy, which can be measured as a voltage A resting neuron has a resting potential of about -70 millivolts. An action potential is triggered when a nerve impulse triggers voltage-gated sodium channels to open, and sodium ions rush into the cell, reversing the charges Now the cytoplasm just inside the membrane becomes positive in charge, and the fluid just outside the membrane becomes negative. Very quickly, the sodium channels close, while voltage-gated potassium channels open, allowing potassium ions to rapidly diffuse out. The plasma membrane returns to being positive on the outside and negative on the inside, and the potassium channels close

IB Exam Question 6. What is the role of active transport in the transmission of nerve impulses by neurones? (1 mark) A. Propagates an action potential by pumping sodium ions across the membrane out of the neurone. B. Propagates an action potential by pumping sodium ions across the membrane into the neurone. C. Initiates the action potential needed for the transmission of an impulse by pumping calcium ions out of the endoplasmic reticulum. D. Establishes the resting potential needed for the transmission of an impulse by pumping sodium and potassium ions across the membrane. Correct answer: D

7. Explain the principles of synaptic transmission. (6 marks) IB Exam Question 7. Explain the principles of synaptic transmission. (6 marks) nerve impulse travels to end of the neuron; this causes synaptic vesicles to fuse with membrane; the vesicles release neurotransmitter molecules into synaptic cleft; these neurotransmitter molecules bind to receptors on next neuron; this causes ion channels to open on that neuron; sodium ions rush in, changing the polarity of the membrane, and an action potential is triggered in the receiving cell