L05 - The Nervous System (LHS)

Homeostasis

The body's ability to maintain stable internal conditions despite external changes.

Nervous System

The body system responsible for sensing changes in the environment, coordinating responses, and regulating physiology.

Central Nervous System (CNS)

Comprised of the brain and spinal cord, responsible for processing and coordinating information.

Peripheral Nervous System (PNS)

Consists of signal-carrying nerves connecting the CNS to the rest of the body.

Brain

Organ responsible for learning, memory retention, balance maintenance, sensory information interpretation, and decision-making.

Neurons

Nerve cells that communicate with each other, with the brain containing an estimated 100 billion neurons.

Spinal Cord

Coordinates involuntary reflexes and serves as the main connection between the PNS and the brain.

Afferent System

Part of the PNS that receives sensory data from receptors and transmits it to the CNS for processing.

Efferent System

Part of the PNS that receives messages from the CNS and transmits them to effector cells to initiate actions.

Receptors

Sensory organs' components that detect environmental changes, with different receptors detecting various stimuli.

Somatic Nervous System

Controls voluntary actions, while the Autonomic Nervous System regulates involuntary functions.

Glial Cells

Non-conducting cells of the nervous system providing support, myelin formation, and protection to neurons.

Nerve Cells (Neuron)

Conducting cells of the nervous system that transmit electrical signals throughout the body.

Dendrites

Branching extensions on neurons that receive signals from other neurons.

Axon

Long extension from the cell body transmitting signals to other cells, often covered by a myelin sheath.

Motor Neuron

Efferent neuron relaying information from the CNS to effectors like muscles, organs, or glands.

Sensory Neuron

Afferent neuron sensing information from the environment and relaying it to the CNS.

Interneurons

Neurons connecting sensory neurons to motor neurons within the body.

Myelin Sheath

Insulating layer around axons formed by glial cells, speeding up signal transmission.nucleus of Schwann cell

Multiple Sclerosis (MS)

Disease affecting the myelin sheath, leading to various symptoms like vision problems and paralysis. Fatigue, loss of balance, partial or compète paralysis, coordination, speech, bladder, bowel, short term memory issues

Astrocytes

Glial cells providing structural and metabolic support to neurons and regulating ion concentrations and neurotransmitters sweep up debris

Reflex Arc

Neural pathway controlling reflex actions, where the spinal cord initiates the response before the brain processes it. Since muscles work in opposing pairs the two signals are sent the first relaxes triceps the second engages biceps

Resting Potential

Neuron's stable negative charge inside compared to the outside, maintained by ion gradients and pumps.

Depolarization

The process of raising the membrane potential during an action potential in a neuron.

Nerve Impulse

The electrical signal that travels along a neuron.

Action Potential

The rapid change in electrical potential across a membrane as a nerve impulse is transmitted.

Repolarization

The phase during which the membrane potential of a neuron is restored after depolarization.

Na+/K+ Pumps

Proteins that help maintain the resting potential of a neuron by pumping sodium ions out and potassium ions in.

Refractory Period

The time following an action potential when a neuron is less sensitive to additional stimuli.

All-or-Nothing Response

• The principle that an action potential either fires completely or not at all. Since action potential is all or nothing in response to stimulus. If threshold potential is not reached (-55mV) the méninge does nothing

• Neuron rests at -70Mv

• Much reach -55 Mv to trigger depolarization

• Reaches peak turns into dépolarisation back to resting state

• Between a refractory period occurs where the neuron is hyperpolarized

Impulse Propagation

• The transmission of the nerve impulse down the axon. The action potential is generated at the axon hillock where an electrical current depolarizes the neighbouring region of the axon membrane

• The impulse travels down the axon as each section of the mentante that reaches its action potential depolarixed the membrane downstream from it

Conduction Speed

The rate at which an action potential travels along an axon, influenced by axon diameter and myelination. The myelin sheath insulates the axon, nodes of rangier are gaps that allow space for ion exchange.

Synaptic Cleft

• The small gap between the axon terminal of one presynaptic and the dendrite of another postsynaptic neuron where neurotransmitters are released.

• Nerve impulse causes neurotransmitters to be released

1 -Neuron

Dendrites

2 - Neuron

Cell body

3 - Neuron

Nucleus

4 - Neuron

Presynaptic cell

5 - Neuron

Myelin sheath

6 - neuron

Axon

7 - Neuron

Signal direction

8 - Neuron

Synapse

9 - Neuron

Postsynaptic cell

Oligodendrocyte

• In the cns

• Are glia that form myelin sheaths around the axons of many vertebrate neurons

Schwann cells

myelinating cell of the PNS and support cells

Synaptic cleft step 1

impulse from action potential opens ion channels for calcium ions

Synaptic cleft step 2

The increased calcium concentration in the axon terminal triggers release of neurotransmitters

Synaptic cleft step 3

Neurotransmitters released from its vesicle and crosses cleft and attaches to a protein receptor

Synaptic cleft step 4

Interaction of neurotransmitter and protein recoepr opens membrane ion channel for sodium

Synaptic cleft 5

Nt either degraded by an enzyme or taken back to presynatoc membrane by transporter or pump