BIOL1050 Reception

week 3

features of a decentralized nervous system

no brain

examples of species with DNS

Starfish (Echinotherms) have nerve rings around their mouths, jellyfish who have a nerve net where signals travel all over the body.

examples of centralized nervous systems

verterbrates, the brain is connected to ganglia, or others transmit signals via nerve cords. Annelids and Anthropods have a more primitive version of a spinal cord called a ventral nerve cord. Humans have a CNS broken down into two parts, the central (brain and spinal cord) and the peripheral (nerves and ganglia that transmit signals to the rest of the body

anatomy, organisation and function of the CNS

controls higher order functions, regulates the input-integration-response model, includes the brain and the spinal cord

the structure, function and anatomy of the PNS

PNS sends signals to the CNS,  includes all the nerves that branch out from the brain and spinal cord to the rest of the body. The functions of the peripheral nervous system include sensing the environment and sending action potentials back to the brain, as well as responding through motor outputs. it can be both sympathetic and parasympathetic

whats the parasympathetic in the PNS?

which drives rest & digest responses

what the sympathetic in the PNS?

controls flight or fight responses

whats the somatic system in the PNS?

for voluntary muscles control via skeletal system

automatic system in the PNS

for involuntary functions like heart rate

what does the enteric system control

 controls digestion and blood flow

what are neurons used for ?

to pass signals between cells, causing gland secretion or motor functions

what are schwann cells used for?

produce Myelin for the PNS,

what are Oligodendrocytes used for?

To produce myelin for the CNS

Ependymal cells

which filter blood plasma to produce cerebral spinal fluid

Astrocytes

help maintain the blood barrier and regulate extracellular fluid

Microglia

 immune cells that survey the CNS for damage

cerebral spinal fluid

supports the brain and spinal cord, which is produced by ependymal cells in the ventricles in the brain. It circulates constantly, supply nutrients and removing waste products.

describe the structure of the CNS

The spinal cord is separated into two horns - the  dorsal (back) horn and the ventral (front horn). The dorsal horn is the entry point for sensory neurons, the ventral horn is the exit point for somatic and autonomic motor neurons. Some also have a lateral horn, which sends signals to the brain and the rest of the body. CSF circulates from the ventricles to the spinal cord and over the brain

what does the forebrain include?

cerebrum and diencephalon

hindbrain

cerebellum and part of the brainstem

midbrain

includes part of the brain stem

Brain stem

which receives and integrates sensory info and sends it to the forebrain

pons and medulla

transmit action potentials between the PNS and higher brain centres and regulates automatic actions like breathing

cerebellum

initiates coordinated movement e.g. hand eye coordination and balance

Thalamus

sensory gatekeeper for the cortex, where sensory info synapses

Hypothalamus

homeostatic control and regulates hormone secretion by endocrine glands

Epthalamus

pineal gland which secretes melatonin to maintain sleep cycles.

whats located in the diencephalon

Thalamus, hypothalamus and Epthalamus

what does the cerebrum contain?

cerebral cortex which controls skeletal muscle coordination, the Basal nuclei which is important for learning movement, and the Corpus callosum which are axons that facilitate communication between hemispheres.

what lobes is the cerebral cortex split into?

frontal, temporal, parietal and occipital lobes

Role of the cerebral cortex?

It executes the input-integration-response pathway, where sensory areas like the somatosensory cortex receive and process info and motor areas like the primary motor cortex transmit instructions to other parts of the body.

what does the Occipital lobe do?

 receives and interprets info from the eyes

what does the Temporal lobe do?

processes sounds and helps recognise faces/words

what does the parietal lobe do?

 handles touch, temp and pain

what does the prefrontal cortex do?

used for higher order thinking like problem solving

Primary Motor Cortex

Sits in the frontal lobe just before the parietal boundary.

Broca's Area

Located in the frontal lobe; helps produce spoken and written language

Wernicke's Area

• Located in the temporal lobe; helps understand the meaning of speech and text

 

what are the 4 stages in sensory processing?

Sensory processing involves four steps: Reception, transduction, transmission and perception.

how do transduction and transmission work?

Covert into electrical signal, where stimuli cause membrane ion channels to open/close creating a shift in membrane potential called sensory transduction (resulting in graded potentials a.k.a receptor potentials).

Sensory transmission sends action potentials to the CNS, where the brain relies on labelled lines to tell stimuli apart.

what does the first order neuron do?

sensory receptor to the spinal cord

what does the secondary receptor neuron do?

signal to thalamus

what does the third order neuron do?

signal from thalamus to cerebral cortex

intensity of a signal is driven by?

 frequency of action potentials and the number of receptors

what are the three ways nervous system encodes stimulus?

intensity, type and location

what do type sensors include?

chemoreceptors (solute levels), mechanoreceptors (touch), Electromagnetic receptors (light/magnetic fields), Thermoreceptors (temp change), nociceptors (pain)

what do location sensors include?

sensory discrimination is based on:

Receptor density

Receptive field size

Cortical representation

We can explore sensory discrimination by comparing how we respond to touch on our hands compared to our own calf.

examples of sympathetic nervous system effects

 increase heart rate, dilate pupils

examples of parasympathetic nervous system effects

reduce heartrate, enlarge pupils

the automatic nervous system is made up of which neurons

postganglionic((synapse with pre at ganglia) , preganglionic (beginning in the CNS) and ganglia.

what enzymes to postganglionic and preganglionic neurons release?

Preganglionic release acetylcholine, while Postganglionic release acetylcholine in parasympathetic or noradrenaline in sympathetic.

where do preganglionic neurons start in the sympathetic divison?

 centre of the spinal cord, linking the thoracic and thumber regions where neurons synapse close to the spinal cord.

where do preganglionic neurons start in the parasympathetic system?

 in the brain stem and sacral region of the spinal cord. These neurons synapse close to the target organ.

what is the difference between ganglionic neurons in the para vs sympathetic nervous system?

The sympathetic nervous system Features short preganglionic neurons and long postganglionic neurons because ganglia sit near the spinal cord. The Parasympathetic nervous system features long preganglionic neurons and short postganglionic neurons because ganglia sit near or inside target organs