Knowt
nervous system
Peripherical Nervous System (PNS)
Nerves → Nervous tissue → Neurons
Central Nervous System (CNS)
Made up of relay neurons
Brain
Spinal Chord
Neurons
Sensory neurons: From sense organs to the Central Nervous System
Its shape is long with a receptor on one end.
Relay neurons: Impulses can travel both ways.
Its shape is small with lots of dendrites and a central nucleus.
Connects the motor and sensory neurons.
Only found in the CNS, and they are multipolar.
Motor neurons: From the central nervous system towards effectors (muscles and glands)
Its shape is long, with dendrites from one end
Impulse (also called action potential)
Is a series of electrical pulses that travel really quickly carrying information towards and from the central nervous system.
an
an
an
parts of the neurons
Dendrites: Extensions that mainly receive and improve synaptic neuronal communication.
Axon: Long fiber that allows a quicker carrying process from neuron to neuron
It is mostly insulated due to a fatty sheath, but where it is not insulated, the impulses can jump from one “node” to another.
Voluntary and involuntary actions
An involuntary action is any action that a body makes without thinking about it and making the conscious decision to do it.
Therefore, a reflex is an involuntary action. But what makes a reflex a reflex is that it always responds to stimuli, it is automatic.
Examples of reflexes:
Blinking
Flinch
reflex arc
Stimulus → Receptor → Sensory Neuron → Co-ordinator (CNS) // Relay neurons → Motor neuron → Efector → Response
Synapse
A method of active transport to communicate neurons between themselves so that they can pass on impulses even though they always have a cleft between them.
Presynaptic neuron: Has vesicles that are carrying the neurotransmitters, the vesicles are triggered by the electrical impulse.
Synaptic cleft.
Postsynaptic neuron: Has receptors with whom specific neurotransmitters bind.
The neurotransmitters that do not bind, are uptaken again into the presynaptic neuron, or broken down by enzymes.
Sense organs
A sense organ is a group of tissues with a specific task, that has a bunch of sensory neurons and receptors responding to a specific stimulus. They are mainly known for the five senses.
Sense organ | Stimulus |
|---|---|
mouth | chemicals (taste) |
nose | chemicals (smell) |
eye | light |
ears | sound and balance |
skin | touch, pain, temperature, and pressure. |
The eye👁️🗨️
The pupil reflex
Mechanism to protect the retina from damage in bright light and to allow vision with dim-light.
Photoreceptors detect the change in the environment’s light conditions.
Dim light | Bright light |
|---|---|
Pupil dilates to enter as much light as possible. | Pupil constricts preventing too much light entering and damaging the retina. |
Radial muscles contract | Radial muscles relaxed. |
Circular muscles relax | Circular muscles contracted. |
Circular and Radial muscels; The iris (circular and radial muscles) and pupil; The cilliary muscles and suspensory ligaments have an ANTAGONISTIC RESPONSE.
Lens’ accommodation
Its purpose is to focus according to the distance of the object willing to be seen.
The Lens is elastic and has a changing shape, relying on how tight the suspensory ligaments are.
The change in lens’ accommodation is mainly causes bythe relaxation or contraction of the ciliary muscles
Near object | Distant object |
|---|---|
Light needs to be more refracted. | Light is less refracted. |
Ciliary muscles contracted | Ciliary muscles relaxed |
Suspensory ligaments slacked | Suspensory ligaments contracted |
Fatter lens | Thinneer lens |
Structure | Function |
|---|---|
Cornea (Scelera) | A transparent lens that refracts light to focus images. |
Iris | Controls the amount of light entering the pupil |
Lens | A transparent disc that changes its shape through accommodation with the help of the suspensory ligaments and ciliary muscles to regulate the light that enters the retina. |
Retina | When light falls on it, rods and/or cones are stimulated and they send impulses. |
Optic nerve | A nerve that carried impulses from the retina towards the brain, producing the images. |
Pupil | A hole that allows light to enter the rest of the eye. |
Why the eye cannot easily identify different colors in low levels of light?
Because the coness (that enable color distinguishment) are not sufficiently stimulated due to low light levels. In contrast, most light in a dim environment is used to stimulate rodes so that the eye can see.
Cells in the retina:
Rods: Sensible to light changes.
Rods are everywhere in the retina except for the blind spot
Cones: Sensible to colors.
Cones are mainly found in the Fovea
nervous system
Peripherical Nervous System (PNS)
Nerves → Nervous tissue → Neurons
Central Nervous System (CNS)
Made up of relay neurons
Brain
Spinal Chord
Neurons
Sensory neurons: From sense organs to the Central Nervous System
Its shape is long with a receptor on one end.
Relay neurons: Impulses can travel both ways.
Its shape is small with lots of dendrites and a central nucleus.
Connects the motor and sensory neurons.
Only found in the CNS, and they are multipolar.
Motor neurons: From the central nervous system towards effectors (muscles and glands)
Its shape is long, with dendrites from one end
Impulse (also called action potential)
Is a series of electrical pulses that travel really quickly carrying information towards and from the central nervous system.
an
an
an
parts of the neurons
Dendrites: Extensions that mainly receive and improve synaptic neuronal communication.
Axon: Long fiber that allows a quicker carrying process from neuron to neuron
It is mostly insulated due to a fatty sheath, but where it is not insulated, the impulses can jump from one “node” to another.
Voluntary and involuntary actions
An involuntary action is any action that a body makes without thinking about it and making the conscious decision to do it.
Therefore, a reflex is an involuntary action. But what makes a reflex a reflex is that it always responds to stimuli, it is automatic.
Examples of reflexes:
Blinking
Flinch
reflex arc
Stimulus → Receptor → Sensory Neuron → Co-ordinator (CNS) // Relay neurons → Motor neuron → Efector → Response
Synapse
A method of active transport to communicate neurons between themselves so that they can pass on impulses even though they always have a cleft between them.
Presynaptic neuron: Has vesicles that are carrying the neurotransmitters, the vesicles are triggered by the electrical impulse.
Synaptic cleft.
Postsynaptic neuron: Has receptors with whom specific neurotransmitters bind.
The neurotransmitters that do not bind, are uptaken again into the presynaptic neuron, or broken down by enzymes.
Sense organs
A sense organ is a group of tissues with a specific task, that has a bunch of sensory neurons and receptors responding to a specific stimulus. They are mainly known for the five senses.
Sense organ | Stimulus |
|---|---|
mouth | chemicals (taste) |
nose | chemicals (smell) |
eye | light |
ears | sound and balance |
skin | touch, pain, temperature, and pressure. |
The eye👁️🗨️
The pupil reflex
Mechanism to protect the retina from damage in bright light and to allow vision with dim-light.
Photoreceptors detect the change in the environment’s light conditions.
Dim light | Bright light |
|---|---|
Pupil dilates to enter as much light as possible. | Pupil constricts preventing too much light entering and damaging the retina. |
Radial muscles contract | Radial muscles relaxed. |
Circular muscles relax | Circular muscles contracted. |
Circular and Radial muscels; The iris (circular and radial muscles) and pupil; The cilliary muscles and suspensory ligaments have an ANTAGONISTIC RESPONSE.
Lens’ accommodation
Its purpose is to focus according to the distance of the object willing to be seen.
The Lens is elastic and has a changing shape, relying on how tight the suspensory ligaments are.
The change in lens’ accommodation is mainly causes bythe relaxation or contraction of the ciliary muscles
Near object | Distant object |
|---|---|
Light needs to be more refracted. | Light is less refracted. |
Ciliary muscles contracted | Ciliary muscles relaxed |
Suspensory ligaments slacked | Suspensory ligaments contracted |
Fatter lens | Thinneer lens |
Structure | Function |
|---|---|
Cornea (Scelera) | A transparent lens that refracts light to focus images. |
Iris | Controls the amount of light entering the pupil |
Lens | A transparent disc that changes its shape through accommodation with the help of the suspensory ligaments and ciliary muscles to regulate the light that enters the retina. |
Retina | When light falls on it, rods and/or cones are stimulated and they send impulses. |
Optic nerve | A nerve that carried impulses from the retina towards the brain, producing the images. |
Pupil | A hole that allows light to enter the rest of the eye. |
Why the eye cannot easily identify different colors in low levels of light?
Because the coness (that enable color distinguishment) are not sufficiently stimulated due to low light levels. In contrast, most light in a dim environment is used to stimulate rodes so that the eye can see.
Cells in the retina:
Rods: Sensible to light changes.
Rods are everywhere in the retina except for the blind spot
Cones: Sensible to colors.
Cones are mainly found in the Fovea
