The Nervous System Flashcards
2 types of nervous system cells
Neurons and glial cells
Neurons
Specialized cells in the nervous system that control behavior, convey sensory information, and signal movement. Their main function is communicate, and they communicate with other neurons and glial cells using neurotransmitters
Glial cells
Support the function of neurons
4 major components of neurons
A soma, dendrites, axon, axon terminal
Soma of neuron
The cell body that contains the nucleus (and DNA). Components in the soma support a neuron’s basic physiological processes. Also contains the mitochondria and the endoplasmic reticulum (ribosomes)
Dendrites
Neurons have many dendrites that branch off of the soma. Dendritic spines grow along the dendritic branches. The dendritic spines and the membranes of dendrites contain proteins called receptors that are activated by neurotransmitters
Axons
Release neurotransmitters for signaling with other neurons. There is usually only one axon that is opposite from the dendrites. The axon begins at the axon hillock. The axon is like a wire that transmits an electrical signal
Axon hillock
The part of the soma where the axon begins
Axon terminal
The axon ends with multiple branches called axon collaterals, which contain the axon terminals. They are also called presynaptic terminals. They contain vesicles of neurotransmitters
Postsynaptic terminal
A part of a dendrite that contains receptors for neurotransmitters
Synaptic cleft
The small space between the axon terminal and the postsynaptic terminal
Synapse
The components that make up the connection between neurons- the axon terminal, postsynaptic terminal, and synaptic cleft
Myelin
Fatty material that acts as insulation for the axon and speeds up action potentials through saltatory conduction
Node of Ranvier
Exposed portion of axon, allows the cell to interact with the extracellular fluid
The language of the brain is
Electrochemical
Interneuron
A neuron with the soma and axon found in the same structure. They transmit signals between sensory and motor neurons and are typically located in the brain and spinal cord
Sensory neurons
Convey sensory information via axons to the central nervous system. They are considered afferent neurons because their axons are going to another structure
Motor neurons
Convey motor information via axons from the central nervous system. They are considered efferent neurons because their axons are coming from a structure
3 types of glial cells
- Oligodendrocytes
- Astrocytes
- Microglial cells
Central nervous system
brain and spinal cord. Sensory activities, memory, and emotions
Peripheral nervous system
connects the CNS with the rest of the body. There are multiple divisions
Broadly, what is the main function of neurons?
Communicating messages
Node of Ranvier
Gaps between the myelin on the axon, where the axon is exposed to extracellular space. The nodes contain sodium channels that can open in response to an action potential and rejuvenate the action potential as it travels down the axon. The action potential slows down at these nodes and speeds up to get through the myelinated sections of the axons
Saltatory conduction
How the action potential travels down the axon. Action potentials slow down as they reach the nodes of Ranvier and speed up as the reach the myelinated sections. This makes it look like the action potential is jumping from node to node. Think of “saltar” in Spanish
Astrocytes
Glial cells that form the blood brain barrier, respond to injury, and regulate neurotransmission. They support neuronal function by acting at synapses during neurotransmission
Oligodendrocytes
Glial cells that form myelin by extending their membranes around axons (in the CNS only). They also hold cells in place. Oligodendrocytes migrate to a certain region of the brain in the juvenile stage but do not migrate after that
Schwann cells
Produce myelin in the peripheral nervous system
Myelin
An insulating layer that surrounds the axons of neurons intermittently. It is mostly composed of lipids. It helps prevents current from leaking out through the axonal membrane, which also prevents the action potential from decaying as it travels down the axon. Myelinated axons conduct action potentials more quickly and efficiently
Microglia
A type of glial cell. Removes cellular waste through phagocytosis. A major part of the immune system in the CNS. There are 2 types- M1 and M2
Multiple sclerosis
Symptoms include motor dysregulation, paralysis, and other symptoms- all result from the degeneration of myelin sheaths
How do astrocytes form the blood brain barrier?
They force endothelial cells to fit tightly together
Endothelial cells
A single layers of cells that lines all blood vessels and lymphatic vessels. It allows your blood and tissues to interact
M1 microglial cells
Release chemicals that promote inflammation. Inflammation is a protective response, but it can damage the blood brain barrier if long term. Inflammation may weaken the blood brain barrier and allow in cells that damage neurons
M2 microglial cells
Release chemicals that reduce inflammation and promote growth and development of cells
What is the broad function of glial cells?
To support the function of neurons. They are one of 2 types of cells found in the brain and outnumber neurons in some regions
Anterior
The front portion of the brain
Posterior
The back portion of the brain
Ventral
The bottom of the brain, which faces toward the stomach- different from inferior because it’s more toward the front
Dorsal
The top of the brain- different from superior because it’s more toward the back
Lateral
Structures near the sides of the brain, away from the midline
Medial
Structures near the middle of the brain
How do you know where the back of the brain is?
The cerebellum is at the back
Superior
The top of the brain (parietal lobe region)
Inferior
The bottom of the brain, down toward the spinal cord
Coronal (frontal) section
Slicing the brain from anterior to posterior- produces a vertical section, like a loaf of bread
Horizontal section
Slicing the brain from dorsal to ventral, making a horizontal section- like slicing a bagel
Sagittal section
Provides lateral views of the brain- facing the sides of the brain from the middle. Cuts the right and left sides of the brain into different parts
2 subsystems of the PNS
- Somatic nervous system
- Autonomic nervous system
Somatic nervous system
Delivers voluntary motor signals from the CNS to the muscles, and conveys sensory information from the body to the CNS. It is made up of motor neurons and sensory neurons
Dorsal root
The dorsal part of the spinal cord, which sensory neurons send information to. Information goes through the dorsal root to the dorsal horn
Ventral horn
The ventral part of the spinal cord that motor signals send information to. Information is sent from the ventral horn to the ventral root to get to the muscles
Autonomic nervous system
Controls involuntary functions like heartbeat, breathing, swallowing, digestion, and sweating. It controls heart muscle, smooth muscle, and exocrine glands to accomplish these functions
3 divisions of the autonomic nervous system
- Sympathetic nervous system
- Parasympathetic nervous system
- Enteric nervous system
Sympathetic nervous system
Fight or flight- prepares the body for rigorous activity and energy expenditure, like for emergency situations. When activated, it increases the heartbeat, inhibits digestion, and opens airways
Parasympathetic nervous system
Rest and digest- dominant during relaxed states. It decreases heartbeat, stimulates digestion, and closes airways. Anti anxiety drugs activate the parasympathetic system
Enteric nervous system
Controls digestion via communication within its system and with the central nervous system
Ganglia
Clusters of neuron cell bodies for neurons in both the sympathetic and parasympathetic nervous systems. They contain a neuron’s soma and dendrites, while the axon extends from the ganglion to a muscle or gland
Preganglionic neurons
A neuron that sends an axon from the spinal cord to a ganglion. Neurons in the spinal cord are an example because they send signals to ganglia
Postganglionic neurons
A neuron whose axon extends from the ganglion to a muscle or gland. It’s called postganglionic because its axon comes after the ganglion. The ganglion sends signals to these neurons
Acetylcholine
The neurotransmitter used by preganglionic neurons to control neurons in the sympathetic and parasympathetic nervous systems. Acetylcholine is released at synapses for postganglionic neurons and makes these postganglionic neurons more active. In turn, the postganglionic neurons release neurotransmitters at their axon terminals, so target muscles or glands have increased or decreased activity, depending on the subdivision targeting them
Enteric nervous system
Consists of 200-600 million neurons found in the gastrointestinal tract. There are also thousands of ganglia located throughout the system. It communicates with the CNS but also handles many of its functions independently, making it unique from other PNS systems
Cerebral cortex
The surface of the brain- has gyri (hills) and sulci (valleys). The brain is divided into left and right hemispheres- structures found in one hemisphere have a matching structure in the other hemisphere. It is divided into 4 lobes, controls higher order functioning, and wraps around the midbrain
3 divisions of the brain
- Hindbrain
- Midbrain
- Forebrain
Hindbrain (2 divisions)
Begins where the spinal cord meets the brain stem (at a structure called the medulla). It consists mostly of the brain stem- medulla, pons, and cerebellum. Divisions- Myelencephalon and Metencephalon (contains 4th ventricle)
Midbrain
Located between the hindbrain and forebrain. Contains the inferior colliculus (auditory processing) and superior colliculus (eye movement). Also called the Mesencephalon. Contains the cerebral aqueduct.
Forebrain (2 divisions)
Contains the cerebral cortex and structures beneath the cerebral cortex, like the corpus callosum, basal ganglia, thalamus, and hypothalamus (limbic system). Divisions- Diencephalon (contains third ventricle) Telencephalon (contains lateral ventricle)
Medulla
Controls the autonomic nervous system. It’s found where the spinal cord meets the hindbrain and looks kind of like a thicker section of the spinal cord. It is responsible for functions like breathing, sneezing, sleep wake cycle, heart rate, and vomiting. Cranial nerves also come from the medulla
Vagus nerve
Tenth cranial nerve- sends and receives signals from the body (heart, liver, lungs, intestines). Both motor and sensory (trachea, larynx, pharynx, external ear). Primary line of communication between enteric nervous system and CNS. It is different from other cranial nerves because it controls and receives sensory information from various internal organs.
Cranial nerves
The medulla sends signals to the cranial nerves- they are still considered peripheral nerves even though they come off of the brain. Cranial nerves are broadly devoted to movement and sensations of the head. There are 12 pairs of them.
Accessory nerve
11th cranial nerve. Motor- sternocleidomastoid and trapezius muscles
Hypoglossal nerve
12th cranial nerve. Motor- muscles of the tongue
Trigeminal nerve
5th cranial nerve. Motor- chewing muscles. Sensory- face, sinuses, teeth
Abducens nerve
6th cranial nerve. Motor- external rectus muscle
Trochlear nerve
4th cranial nerve. Motor- superior oblique muscle
Oculomotor nerve
3rd cranial nerve. Motor- all eye muscles except those supplied by the Abducens and Trochlear nerves (6 and 4)
Optic nerve
2nd cranial nerve. Sensory- eye
Olfactory
1st cranial nerve. Sensory- nose
Facial nerve
7th cranial nerve. Motor- muscles of the face
Vestibulocochlear nerve
8th cranial nerve. Sensory- inner ear
Glossopharyngeal nerve
9th cranial nerve. Motor- pharyngeal musculature. Sensory- posterior part of tongue, tonsil, pharynx
Suppression of the medulla
The medulla controls vital functions like breathing, heart rate, and vomiting. For this reason, damage to or suppression of the medulla can be life threatening. Narcotics and CNS depressants (like alcohol) suppress the function of the medulla, and mixing them can have synergistic effects. Even mixing safe amounts of 2 different depressants can be very dangerous.
Hypothalamus
Found in the lower region of the brain (the forebrain). Maintains homeostasis, regulates the pituitary gland and the pineal gland, regulates body temperature, also controls motivation (the 4 Fs). Has a direct influence on the medulla and the ANS
Pineal gland
Part of the endocrine system, regulated by the hypothalamus. Regulates melatonin
Pituitary gland
Part of the endocrine system, regulated by the hypothalamus. Releases many hormones into the bloodstream, affecting organ functions. Regulates reproductive systems, thyroid function, growth, water absorption in the kidneys, hunger, and thirst
4 Fs of survival
Functions of the hypothalamus. Feeding, fighting, fleeing, mating
General rule of brain damage
The lower in the brain the damage is, the more dangerous it is
Limbic system
A series of structures that form a ring around the thalamus and hypothalamus. 7 structures- Amygdala, nucleus accumbens, thalamus, cingulate gyrus, basal ganglia, hippocampus, hypothalamus. Contains many structures that are involved in emotional processing
Amygdala
Limbic system structure that facilitates fear and aggression- many drugs that reduce anxiety decrease the activity of neurons in the amygdala. Gives emotional valence to objects or events- may fire for happy things as well.
Nucleus accumbens
Limbic system structure found adjacent and anterior to the amygdala. It is the brain’s reward center. The nucleus accumbens plays a role in the development of craving and is part of what makes a drug pleasurable- there are variations in whether a person likes a specific drug. Distinct structural and molecular alterations in the core of the nucleus accumbens separate craving from motivation or ambition
Craving vs motivation/ambition
Distinct structural and molecular alterations in the core of the nucleus accumbens separate craving from motivation or ambition. Ambition and motivation leads to adaptive behavior, propels our goals and dreams. Craving lead to destructive behavior and consequences, goals and dreams derailed
Thalamus
Limbic system structure that is next to and adjacent to several important structures- looks like a peach and is a good landmark. It is the sensory relay center in the brain and controls the interpretation of ambiguous figures, like the Necker cube. Routes sensory information to appropriate lobes
Basal ganglia
Limbic system structure that stabilizes voluntary movements, controls learned motor movements and instrumentally learned behaviors- how to do things automatically (drive a car, type on a keyboard, and inject an IV drug). Doing an automatic activity well is associated with a sense of intrinsic joy- similar to how carrying out a drug related ritual is associated with pleasure. Drug taking behavior is highly ritualized. The substantia nigra regulates activity in the basal ganglia
Hippocampus
It has a major role in learning and memory. It is a plastic and vulnerable structure that gets damaged by a variety of stimuli. Studies have shown that it also gets affected in a variety of neurological and psychiatric disorders
Cingulate gyrus
Limbic system structure involved in processing emotions and behavior regulation. It also helps to regulate autonomic motor function.
Occipital lobe
The posterior part of the cerebral cortex, processes visual information
Temporal lobe
Anterior to the occipital lobe, at the level of your temples, deals with auditory processing and speech processing. Also processes certain aspects of vision, like shape and color analysis.
Parietal lobe
Above the temporal love at the top of the skull- deals with explicit, planned motor movement. Includes the somatosensory cortex (touch information).
Frontal lobe
At the anterior of the brain, controls decision making and movement. The prefrontal cortex is the most anterior part of the lobe and integrates sensory input. It is also where the signal to produce movement occurs. Also deals with morality, economic decision making, planning- differentiates humans from other species
Cerebellum
Facilitates balance and the timing of movements
