hbs unit 2.1
central nervous system: the brain and spinal cord
peripheral nervous system:nerves that branch out from the brain and spinal cord
cerebrum: the largest part of the brain, responsible for higher brain functions such as thought, action, and sensory processing.
Frontal Lobe: Involved in reasoning, planning, movement, and problem-solving. It is also responsible for higher cognitive functions and emotional regulation.
Parietal Lobe: Processes sensory information from the body; it is responsible for spatial awareness and navigation.
Temporal Lobe: Associated with processing auditory information and is important for memory and understanding language.
Occipital Lobe: Primarily responsible for visual processing and interpreting visual information from the eyes.
cerebellum: the part of the brain located at the back of the skull, responsible for coordination of voluntary movements, balance, and posture.
Brain Stem: The part of the brain that connects the brain to the spinal cord; it plays a role in involuntary vital functions. The brain stem also regulates the sleep-wake cycle and is involved in the transmission of signals between the brain and the rest of the body.
Pons: links your brain to your spinal cord. handles all of your unconscious movements and processes.
cranial nerve I | Also called the olfactory nerve, it relays information about the sense of smell. |
cranial nerve II | Also called the optic nerve, it relays information about the sense of sight. |
cranial nerve III | Also called the oculomotor nerve, it relays information so the eye can move. |
cranial nerve IV | Also called the trochlear nerve, it enables eye movement. Specifically, it controls the ability to look down and move your eyes toward your nose. |
cranial nerve V | Also called the trigeminal nerve, it is in charge of sensation to the face and controls the muscles of mastication (chewing). |
cranial nerve VI | Also called the abducens nerve, it enables eye movement. Specifically, it controls the ability to move your eyes away from your nose. |
cranial nerve VII | Also called the facial nerve, it is in charge of expression. In Unit 1, you learned about Bell’s palsy. This temporary facial palsy is often caused by injury or disease to the facial nerve. |
cranial nerve VIII | Also called the vestibulocochlear nerve, it relays hearing information and is in charge of balance. |
cranial nerve IX | Also called the glossopharyngeal nerve, it is responsible for oral sensation, taste, and salivation. |
cranial nerve X | Also called the vagus nerve, it is the longest nerve in the body and controls heart rate and blood pressure. |
Optic Chiasm: structure at the base of the brain where the optic nerves partially cross, allowing visual information from the right half of the visual field to be processed in the left hemisphere, and information from the left visual field to be processed in the right hemisphere.
Olfactory bulb: A structure located at the base of the brain, responsible for processing the sense of smell.
Broca's Area: Located in the frontal lobe of the brain, Broca's area is crucial for speech production and language processing. Damage to this area can result in Broca's aphasia, characterized by difficulty in forming complete sentences and speaking fluently, although comprehension often remains intact.
Wernicke's Area: Found in the temporal lobe, Wernicke's area is essential for language comprehension. Individuals with damage to this area may produce fluent but nonsensical speech (Wernicke's aphasia), struggling to understand spoken and written language.
Vision - Occipital lobe
Muscle coordination - Cerebellum
Breathing - Brainstem (specifically, the medulla oblongata)
Happiness - Limbic system (including the amygdala and nucleus accumbens)
Language understanding - Wernicke's area (typically located in the left temporal lobe)
Thirst and hunger - Hypothalamus
Speech production - Broca's area (typically located in the left frontal lobe)
Movement - Motor cortex (located in the frontal lobe)
Smell - Olfactory bulb (part of the limbic system)
Reasoning - Prefrontal cortex
Long-term memory - Hippocampus (part of the limbic system)
Hearing - Auditory cortex (located in the temporal lobe)
Bodily sensations, such as touch, temperature, and pain - Somatosensory cortex (located in the parietal lobe)
Taste - Gustatory cortex (located in the insular or frontal lobe)
Blood pressure regulation - Brainstem (medulla oblongata)
Sleeping and waking - Hypothalamus (specifically the suprachiasmatic nucleus)
Balance - Cerebellum and inner ear (vestibular system)
Problem-solving - Prefrontal cortex
Stress - Amygdala and hypothalamus
neurons | Primary signaling cells of the nervous system. Neurons send and receive electrical and chemical signals to communicate with each other in the nervous system and with other types of cells in the body. |
glial cells | Cells in the nervous system that provide protection and maintain homeostasis for neurons. |
Myelin and the Central Nervous System 🧠
Myelin is a cholesterol derivative that insulates the axon, allowing for faster transmission of signals. It is produced by glial cells, also known as support cells, in the central nervous system.
"Myelin is like a fatty insulation that surrounds the axon, allowing signals to jump from node to node, rather than having to travel the entire length of the axon."
Without myelin, signals would have to travel through each ion channel, which is a much slower process. This is why demyelination, such as in Multiple Sclerosis (MS), can cause problems with neural function.
Multiple Sclerosis (MS) 🤕
MS is a disorder that affects the central nervous system, causing demyelination of neurons. This can lead to problems with neural function, including numbness, weakness, and vision problems.
Symptoms of MSDescription | |
Numbness or weakness | Loss of sensation or strength in limbs |
Vision problems | Blurred vision, double vision, or loss of vision |
Fatigue | Feeling tired or exhausted |
Cognitive problems | Difficulty with concentration, memory, or processing speed |
Types of Neurons 🧬
There are three main types of neurons: sensory neurons, motor neurons, and interneurons.
Sensory Neurons 🤔
Sensory neurons are responsible for transmitting information from sensory receptors to the central nervous system.
Characteristics of Sensory NeuronsDescription | |
Cell body location | Close to the spinal cord |
Dendrites | Short and small |
Axon | Long and thin |
Function | Transmit sensory information to the central nervous system |
Motor Neurons 💪
Motor neurons are responsible for transmitting information from the central nervous system to muscles.
Characteristics of Motor NeuronsDescription | |
Cell body location | Close to the spinal cord |
Dendrites | Small and short |
Axon | Long and thin |
Function | Transmit motor information to muscles |
Interneurons 🤝
Interneurons are responsible for transmitting information between different parts of the central nervous system.
Characteristics of InterneuronsDescription | |
Cell body location | Varies |
Dendrites | Long and branching |
Axon | Varies |
Function | Transmit information between different parts of the central nervous system |
Reflex Arcs 🔄
A reflex arc is a neural pathway that allows for rapid response to stimuli. It consists of five parts:
Sensory receptor: Detects the stimulus
Sensory neuron: Transmits the signal to the spinal cord
Interneuron: Processes the signal in the spinal cord
Motor neuron: Transmits the signal to the muscle
Muscle: Responds to the stimulus
"A reflex arc is like a quick response team that allows the body to react rapidly to stimuli, without needing to think about it."## Pain Perception 🤕
Pain is a perception that people feel in lots of parts of the brain. It is not just a simple sensation, but rather a complex process that involves multiple brain regions and neurotransmitters.
Pain Receptors
Pain receptors are specialized nerve endings that detect painful stimuli, such as heat, cold, or pressure. These receptors are found in the skin and other tissues and are responsible for transmitting pain signals to the brain.
The Role of the Brainstem
The brainstem plays a crucial role in pain perception. It is the part of the brain that processes pain signals and sends them to other parts of the brain for further processing.
CIPA: A Disorder of Pain Perception
CIPA (Congenital Insensitivity to Pain with Anhidrosis) is a rare disorder that affects the ability to feel pain. People with CIPA have a mutation in the gene that codes for the pain receptor, which makes them insensitive to pain.
Characteristics of CIPA
Insensitivity to pain
Inability to sweat
Increased risk of injury due to lack of pain perception
The Speed of Pain Signals
Pain signals are one of the slowest traveling neurons in the body. This means that there is a delay between the time a painful stimulus is applied and the time it is perceived by the brain.
Chemical Blockers of Pain
There are chemicals that can block pain receptors, such as endorphins and adrenaline. These chemicals can be released in response to stress or injury and can help to reduce pain perception.
Endorphins and Adrenaline
Endorphins: natural painkillers that are released by the body in response to stress or injury
Adrenaline: a hormone that is released by the body in response to stress or injury and can help to block pain receptors
The Role of the Sympathetic Nervous System
The sympathetic nervous system is responsible for the "fight or flight" response, which is characterized by the release of adrenaline and other stress hormones. This system can also play a role in pain perception by releasing chemicals that block pain receptors.
Synapses and Neurotransmitters 📦
A synapse is the gap between two neurons where chemical signals are transmitted from one neuron to another.
The Structure of a Synapse
ComponentDescription | |
Presynaptic neuron | The neuron that releases the neurotransmitter |
Postsynaptic neuron | The neuron that receives the neurotransmitter |
Synaptic cleft | The gap between the two neurons |
Neurotransmitter | The chemical signal that is released by the presynaptic neuron and binds to receptors on the postsynaptic neuron |
The Process of Neurotransmission
"When one neuron talks to the next neuron or muscle, it's called a synapse. The action ascending neural transfer is a synapse."
The presynaptic neuron releases a neurotransmitter into the synaptic cleft.
The neurotransmitter binds to receptors on the postsynaptic neuron.
The binding of the neurotransmitter to the receptor causes a change in the electrical properties of the postsynaptic neuron.
This change in electrical properties can cause the postsynaptic neuron to fire an action potential.
Research and Histology 🔬
Clinical Researcher vs. Experimental Researcher
Type of ResearcherDescription | |
Clinical Researcher | Conducts research on human subjects to develop new treatments or therapies |
Experimental Researcher | Conducts research in a laboratory setting to understand the underlying mechanisms of a phenomenon |
Histology of a Neuron
"All the little dots are support cells called glial cells."
Cell body: the central part of the neuron where the nucleus is located
Dendrites: the branching extensions of the neuron that receive signals from other neurons
Axon: the long, thin extension of the neuron that carries signals away from the cell body
Support Cells
Type of Support CellDescription | |
Oligodendrocytes | Provide myelin to neurons in the central nervous system |
Schwann cells | Provide myelin to neurons in the peripheral nervous system |
Astrocytes | Provide support and nutrients to neurons |
Microglia | Act as immune cells in the central nervous system |
Ependymal cells | Line the ventricles and central canal of the spinal cord |
Choroid plexus cells | Produce cerebrospinal fluid in the ventricles |
There are several types of cells in the human body, including:
Astrocytes: a type of support cell
Cortical cells: found in the cortex of the brain
Glial cells: a type of support cell
Unipolar cells: found in the cerebellum, these cells have one extension
Bipolar cells: have two extensions
Multipolar cells: have multiple extensions
📝 Neuron Models
When drawing neuron models, be sure to include the following components:
ComponentDescription | |
Dendrites | Receive signals from other neurons |
Cell Body | Contains the nucleus and is responsible for protein synthesis |
Axon | Transmits signals away from the cell body |
Axon Terminal | Releases neurotransmitters into the synapse |
📚 Support Cells
The following support cells are found in the human body:
Cell TypeJob | |
Astrocytes | Provide nutrients and oxygen to neurons |
Oligodendrocytes | Produce myelin, which insulates and protects axons |
Microglia | Act as immune cells and remove pathogens and debris |
Ependymal cells | Line the ventricles and central canal of the spinal cord |
Choroid plexus cells | Produce cerebrospinal fluid |
🤝 Reflex Arc
The reflex arc is a pathway that allows for rapid response to stimuli. The five parts of the reflex arc are:
Receptor: detects changes in the environment
Sensory neuron: transmits signals from the receptor to the spinal cord
Interneuron: processes information and sends signals to the motor neuron
Motor neuron: transmits signals from the spinal cord to the effector
Effector: responds to the stimulus (e.g. muscle contraction)
📝 Assessment and Treatment
When assessing a patient who has fallen, consider the following steps:
Check for injuries and provide basic first aid
Assess the patient's level of consciousness and responsiveness
Check for any signs of neurological damage or impairment
Provide treatment and stabilization as needed
Electricity in the Neuron 🌐
The human body is made up of electrical beings, with moving charges that send messages throughout the body. This concept is similar to the wires in the walls, where flipping a switch sends a message to turn on the lights.
Action Potential 💡
Action potential is the sudden reversal of the overall charge of the inside and outside of a cell, creating an electrical signal or nerve impulse that travels along the axon.
Resting Potential 📉
The resting potential is the state of the cell when it is not being stimulated, with a negative charge of -70 millivolts. This is maintained by the sodium-potassium pump, which moves 3 sodium ions out of the cell and 2 potassium ions into the cell.
Depolarization ⚡️
Depolarization is the change in charge that occurs when a neuron receives a signal, causing the sodium channels to open and allowing sodium ions to rush into the cell. This makes the inside of the cell more positive.
Repolarization 🔄
Repolarization is the process of the cell returning to its resting potential, where the potassium channels open and potassium ions move out of the cell, making the inside of the cell more negative again.
Ion Channels and the Sodium-Potassium Pump 🚪
Ion channels are protein channels that allow ions to move across the membrane, while the sodium-potassium pump is a specialized protein that moves sodium and potassium ions back to their original sides of the membrane.
Ion ChannelFunction | |
Sodium Channel | Allows sodium ions to move into the cell |
Potassium Channel | Allows potassium ions to move out of the cell |
Sodium-Potassium Pump | Moves 3 sodium ions out of the cell and 2 potassium ions into the cell |
The Process of Action Potential 📈
Threshold: The voltage-gated channel reaches threshold, causing the sodium channel to open.
Depolarization: Sodium ions rush into the cell, making the inside of the cell more positive.
Repolarization: The potassium channel opens, allowing potassium ions to move out of the cell, making the inside of the cell more negative again.
Resting Potential: The sodium-potassium pump maintains the resting potential of -70 millivolts.
"The sodium-potassium pump is like a little engine that keeps the cell's charge in balance, moving sodium and potassium ions back to their original sides of the membrane."## 📝 Action Potential and Neurotransmission
Depolarization and Repolarization
Depolarization is the process by which the sodium gate opens, allowing positively charged sodium ions to rush into the cell. This is the "flipping of the charges" that generates electricity and propagates the signal down the axon.
Repolarization, on the other hand, is the process by which the potassium gate opens, allowing positively charged potassium ions to rush out of the cell. This helps to restore the cell's resting potential.
ProcessIon MovementEffect | ||
Depolarization | Sodium ions rush in | Signal propagates down the axon |
Repolarization | Potassium ions rush out | Resting potential is restored |
Action Potential
The action potential is the electrical impulse that travels down the axon, allowing the signal to be transmitted from one neuron to another.
"The action potential is an all-or-nothing phenomenon. Either it happens or it doesn't."
Neurotransmission
Neurotransmission is the process by which the signal is transmitted from one neuron to another. This occurs at the synapse, the small gap between the two neurons.
The Synaptic Cleft
The synaptic cleft is the small space between the sending cell (axon terminal) and the receiving cell (dendrite).
Neurotransmitters
Neurotransmitters are chemical signals that are released by the sending cell and bind to receptors on the receiving cell.
NeurotransmitterEffect | |
Excitatory (e.g. acetylcholine) | Increases the likelihood of an action potential |
Inhibitory (e.g. GABA) | Decreases the likelihood of an action potential |
Graded Potential
A graded potential is the change in the electrical potential of the receiving cell that occurs when a neurotransmitter binds to a receptor.
"A graded potential is the fact that you can get different neurotransmitters bonded to different receptors throughout the whole region. Sometimes you could be getting more negative, and sometimes you could be getting more positive."
Threshold Potential
The threshold potential is the level of depolarization required for an action potential to occur. This is typically around -55mV.
TermDefinition | |
IPSP | Inhibitory Postsynaptic Potential |
EPSP | Excitatory Postsynaptic Potential |
Neurotransmitter Regulation
Neurotransmitters can be regulated by various factors, including the presence of inhibitory or excitatory neurotransmitters.
ADHD and GABA
GABA (gamma-aminobutyric acid) is an inhibitory neurotransmitter that helps to regulate the activity of neurons. Individuals with ADHD (Attention Deficit Hyperactivity Disorder) often have lower levels of GABA, leading to increased neuronal activity and difficulty with focus and attention.